The organic gel-thermal reduction process was successfully used for the preparation of magnetic metal Ni, Fe, Fe-Ni fine fibers from raw materials of citric acid or lactic acid and metal salts. Ni, Fe and Fe-Ni fine fibers synthesized were featured with diameters of around 1 μm and lengths of as long as 2 m for Ni fibers, 0.5 m for iron fibers, 1 m for Fe-Ni fibers. The structure, thermal decomposition process and morphologies of the gel precursors and fibers derived from thermal reduction of these gel precursors were characterized by FTIR, XRD,TG/DSC and SEM, respectively. The gel spinnability largely depends on molecular structures of metal-carboxylate complexes formed in the gel. It is reasoned that these gels consist of linear-type structural molecules [(C6H6O7)Ni]n or [(C6H5O7)2Ni3] for the nickel citrate gel, [(C3H5O3)3Fe] for the ferric lactate gel, [(C6H5O7)5(NiFe)3] for the iron-nickel citrate gel respectively and the gels obtain showed a good spinning performance.
Tribological behaviours of Ti-6Al-4V alloy pins sliding against GCr15 steel discs over a range of contact pressures (0.33–1.33 MPa) and sliding velocities (30–70 m/s) were investigated using a pin-on-disc tribometer under unlubricated conditions. The wear mechanisms and the wear transition were analyzed based on examinations of worn surfaces using SEM, EDS and XRD. When the velocity increases, the friction coefficient and the wear rate of the Ti-6Al-4V alloy show typical transition features, namely, the critical values of sliding velocities for 0.33 and 0.67 MPa are 60 and 40 m/s, respectively. The experimental results reveal that the tribological behaviours of Ti-6Al-4V alloys are controlled by the thermal-mechanical effects, which connects with the friction heat and hard particles of the pairs. A tribolayer containing mainly Ti oxides and V oxides is formed on the worn surface of Ti-6Al-4V alloy.
The microstructures and properties of coating from cemented carbide on the substrate of H13 by vacuum powder sintering were studied. The effect of sintering temperature on the microstructures of coating was discussed. The interface characteristics between coating and H13 steel substrate, microhardness distribution and wear resistance in the coating were analyzed. The coating from cemented carbide with thickness of 1–3 mm by vacuum powder sintering at temperature ranging from 1280 °C to 1300 °C was obtained. The experimental results indicated that the coating with microhardness of HV1600 favorable to wear resistance is strongly bonded with the H13 steel substrate by mutual diffusion and penetration of Fe,Cr,Mo,V in substrate towards the coating and W,Co,Ni in coating towards the substrate.
A novel one-step semisolid processing technique, the rheo-diecasting (RDC) process, was developed, which adapts in situ creation of semisolid metal slurry with fine and spherical solid particles followed by direct shaping of the slurry into a near-net shape component using the existing cold chamber diecasting process. The RDC process was applied to process A356 and A380 aluminum alloys. The resulting microstructures and mechanical properties of RDC products under as-cast and various heat treatment conditions were analyzed. The experimental results show that the RDC samples have an extremely low porosity, a fine and uniform microstructure throughout entire casting, and consequently much improved strength and ductility in the as-cast condition. The strength of RDC A356 alloy can be substantially improved under T5 and T6 heat treatments without loss of ductility.
The novel sandwich composites were prepared by sandwiching a polyvinylidene fluoride/Tb-Dy-Fe alloy composite (PVDF/Terfenol-D) between polyvinylidene fluoride/lead zirconate titanate composites (PVDF/PZT). The maximum magnetoelectric effect voltage coefficient, (dE/dH)33max, of the sandwich composites is higher than that of three-phase composites at their own optimal loading level of Terfenol-D. This is attributed to less interface relaxations of strain and better polarization of the sandwich composites. When the volume fraction of Terfenol-D is higher than 0.10, no coupling interaction for three-phase composites could be observed, but (dE/dH)33max of sandwiched composites still reached 20 mV/(cm·Oe). At high magnetic field intensity, the magnetoelectric effect voltage coefficient, (dE/dH)33, of sandwich composites is higher than that of three-phase composites; at low magnetic field intensity, (dE/dH)33 of sandwich composites is lower than that of three-phase composites. At their resonance frequency, the (dE/dH)33max of the sandwich composites and the three phase composites are 150 mV/(cm·Oe) and 42 mV/(cm·Oe), respectively. This significant increase of (dE/dH)33max at resonance frequency confirms the improvement of maximum magnetoelectric effect coefficient via sandwich-structured composites.
Nanoscale thick amorphous Ni-Cr alloy thin films were fabricated by low-energy ion beam sputtering technology; then the as-deposited samples experienced rapid thermal process to realize the transformation from amorphous to crystalline state. The film thickness was measured with α-stylus surface profiler, the structure and the compositions of the films were confirmed by low angle X-ray diffraction and scanning auger electron microprobe respectively, and the surface topography was characterized by scanning electron microscope and scanning probe microscope. Electrical property of the films was measured by four-point probe. The experimental results illustrate that the combined processes of ion beam sputtering and rapid thermal process are effective for fabrication nanoscale Ni-Cr alloy thin film with good properties.
By means of scanning electron microscopope and X-ray diffraction, microstructural evolution of well-aligned ZnO nanorod array films was studied. The films were prepared on a glass using direct deposition method in an aqueous solution. The experimental results show that the highly oriented rods grew from the randomly oriented crystals. Those rod-like randomly oriented crystals began to impinge on other neighboring crystals and their growth became physically limited; only the rods perpendicular to the substrate were allowed to grow freely. This kinetically controlled nucleation and growth would be responsible for producing the uniformly oriented nanorods. During the ZnO rods’ growth, the topology of their top faces changed from flat, prismatic to finally flat.
By applying the reinforcing and toughening effect of calcium carbonate (CaCO3) nano-particles on polypropylene, foam sheets of good performance were successfully fabricated by extrusion. The equipment and conditions of the extrusion were explored. The mechanical properties of the produced foam sheets were tested. The effect of CaCO3 nano-particles on the mechanical properties and the cellular structure of the sheets was comprehensively studied. The experimental results show that the optimum content of CaCO3 nano-particles in the composite material was ∼4wt%. At this content, the nano-particles were well dispersed in the substrate, and the composite material had maximum tensile strength and impact strength. Surface treatment of the nano-particles only affected the impact strength of the composite material. CaCO3 micro-particles, on the other hand, showed little effect on the properties of the composite material when the micro-particles content was less than 5 wt%. At a content higher than 5wt%, the properties of the composite material significantly worsened.
A thimble zirconia oxygen sensor was prepared with YSZ. The surfaces of the Pt electrode, electrolyte and their interface were observed with a scanning electron microscope (SEM).The sensor was examined with engine bench test to evaluate the essential performance. The basic function such as electromotive force output and response time was discussed. The oscillograph trace was also obtained and analyzed with four different frequencies. The experimental results reveal that the oxygen sensor has high performances meeting the demands of practical applications.
The spores of Ganoderma lucidum were ground and broken to ultrafine particles by high speed centrifugal shearing(HSCS) pulverizer. The characteristics of Ganoderma lucidum spores were analyzed by scanning electron microscope (SEM), Fourier transform infrared spectrophotometry (FTIR). Ultraviolet-visible pectrophotometer was used to determine the extraction ratio of aqueous solubility polysaccharide between the raw and broken spores. The immunological function on the mice before and after the breaking of spores was investigated. The experimental results show that after being ground, the sporoderm-broken ratio reachs 100%, the original active ingredients of ganoderma lucidum spores do not change, and the extraction ratio of aqueous solubility polysaccharide is greatly increased by 40.08%. The broken spores show much higher immunological activity comparing with original spores of Ganoderma lucidum.
Fine particles of zinc-cerium oxides (ZCO) used as an ultraviolet filter were prepared via combustion synthesis route. The catalytic activity, UV-shielding performance, surface modification and application of ZCO in polyester varnish were discussed in detail. The experimental results indicate that the photo-catalytic activity of ZCO is much smaller than these of ZnO and TiO2; the oxidation catalytic activity of ZCO is far lower than that of CeO2; the ZCO has shown excellent ultraviolet absorption in the range of UV; addition modified ZCO (MZCO) into polyester will enhance the UV-shielding capability of polyester.
Nanometer RuO2-SnO2 was synthesized by the citrate-gel method using RuCl3, SnCl4 as cation sources, citric acid as complexing agent and anhydrous ethanol as solvent. The structures of the derived powders were characterized by thermogravimetric and differential thermal analysis, X-ray diffraction, transmission electron microscope, and Brunauer-Emmett-Teller surface area measurement. The pure, fine and amorphous powders was obtained at 160 °C. The materials calcined at above 400 °C were composed of rutile-type oxide phases having particle sizes of fairly narrow distribution and good thermal resistant properties. By adding SnO2 to RuO2, the Ru metallic phase can be effectively controlled under a traditional temperature of preparation for dimensional stable anode.
TiC films deposited by rf magnetron sputtering followed by Ar+ ion bombardment were irradiated with a hydrogen ion beam. X-ray photoelectron spectroscopy (XPS) was used for characterization of the chemical bonding states of C and Ti elements of the TiC films before and after hydrogen ion irradiation, in order to understand the effect of hydrogen ion irradiation on the films and to study the mechanism of hydrogen resistance of TiC films. Conclusions can be drawn that ion bombardment at moderate energy can cause preferential physical sputtering of carbon atoms from the surface of low atomic number (Z) material. This means that ion beam bombardment leads to the formation of a non-stoichiometric composition of TiC on the surface. TiC films prepared by ion beam mixing have the more excellent characteristic of hydrogen resistance. One important cause, in addition to TiC itself, is that there are many vacant sites in TiC created by ion beam mixing. These defects can easily trap hydrogen and effectively enhance the effect of hydrogen resistance.
(Ba0.4Pb0.3)Sr0.3TiO3 thin films were fabricated via pulsed laser deposition (PLD) technique on Pt/TiO2/SiO2/Si substrate. The crystallization of the films was characterized by XRD and FSEM, and the experimental results suggested deposition parameters, especially the deposition temperature was the key factor in forming the perovskite structure. The dielectric properties of the film deposited with optimized parameters were studied by an Agilent 4294A impedance analyzer at 1 MHz. The dielectric constant was 772, and the loss tangent was 0.006. In addition, the well-shaped hysteresis loop also showed that the film had a well performance in ferroelectric. The saturated polarization P s, remnant polarization P r and coercive field E c were about 4.6 μC/cm2, 2.5 μC/cm2 and 23 kV/cm (the coercive voltage is 0.7 V), respectively. It is suggested the film should be a promising candidate for microwave applications and nonvolatile ferroelectric random access memories (NvFeRAMs).
The photorefractive (PR) performance of an organic/inorganic hybrid polymer composite sensitized by CdS nanoparticles, combining poly(N-vinylcarbazole) (PVK), the second-order optically nonlinear chromophore 1-n-butoxy-2-methyl-(4-p-nitropheylazo)benzene (BMNPAB) and 9-ethylcarbazole (ECZ) was studied. It was confirmed that the CdS colloidal particles had a nanoscale size and quantum confinement effect adopting transmission electron microscopy and UV-Vis absorption spectroscopy. The addition of CdS nanoparticles as a photosensitizer in PVK will be significant enhancement of photoconductivity because of the high photocharge generation quantum efficiency and high charge transport to conducting polymer. The polymer composite film exhibited PR effect with a method of two-beam coupling experiment. And an asymmetric two-beam coupling gain of 45.8 cm−1 without applied electric filed is obtained at 632.8 nm wavelength.
ZnO nanopowders were prepared by oxidizing Zn vapor in the atmosphere of mixture gas of Ar and O2 at low pressure. Tetrapod nanowhiskers synthesized at a pressure of 1.6 kPa show pure ZnO feet and Zn phase in the core of the nanopowder. The ellipsoid ZnO nanoparticles were produced at the pressure of 10 kPa. The photodegradation rate of aniline and chemical oxygen demand removal demonstrate that the photocatalytic efficiency of Zn/ZnO nanowhiskers with UV irradiation is higher than that of ZnO nanoparticles. The tetrapod morphology and Zn phase inside nanowhiskers play key a role in photodegradation process.
A stable epoxy emulsion was prepared with epoxy resin (EP) as raw material, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as modifier and benzoyl peroxide as initiator. By criterion of yield of the copolymer AMPS-EP, water-solubility, change of the acid value and intrinsic viscosity [η] along with reaction time, the copolymerization course was deduced. It is found that during the process, AMPS takes part in both the grafting copolymerization with epoxy principal chain and the ring-opening polyaddition with epoxy group. It is also discovered that the yield of AMPS-EP and water dispersing varies with reaction time. When it reaches 1.5 h, AMPS-EP can obtain good water-solubility; but the water-solubility will go bad gradually if it exceeds 3.5 h. IR spectrum analysis indicates that partial epoxy group partially remains and the others create sulfonic ester.
The adsorption behavior and mechanism of D113 resin for Dy(III) was investigated by using the method of resin adsorption. Experimental results show that the optimum medium pH of adsorption of D113 resin for Dy3+ is pH=6.00 in the HAc-NaAc medium. The static adsorption capacity of D113 resin for Dy3+ is 292.7 mg·g−1. The optimum eluant is 0.5 mol·L−1 HCl. The adsorption rate constant is k 298=6.8×10−6s−1. The apparent activation energy of D113 resin for Dy(III) is 14.79 kJ·mol−1. The adsorption behavior of D113 resin for Dy(III) obeys the Freundlich isotherm. The adsorption parameters of thermodynamic are ΔH=14.48 kJ·mol−1, ΔS=54.69 J·mol−1·K−1, ΔG=−1.82 kJ·mol−1.The adsorption mechanism of D113 resin for Dy3+ was confirmed by chemical analysis and IR spectra.
Mesoporous silica films embedded with Ag nanoparticles were directly synthesized by a solgel dip-coating process, combining alkyl (ethylene oxide) surfactant as temple and tetraethoxysilane as inorganic precursor. The addition of Ag+ ion to the reaction sol was prior to the formation of films, followed by the heat treatment at 150 °C led to the creation of Ag nanoparticies. The formation of Ag nanoparticles and the change of its surface plasma resonance absorption were characterized by Uv-vis. The small angle XRD test indicated that the films had an ordered hexagonal mesoporous structure, of which the unit cell parameter was about 4.26 nm. The TEM images and EDS spectra of the samples have directly verified the presence of mono-dispersed Ag nanoparticles within the films, due to the confine effects of mesopores.
The surface properties of kaolinite were determined using density functional theory discrete variational method (DFT-DVM) and Gaussian 03 program. A SiO4 tetrahedral hexagonal ring with two Al octahedra was chosen to model the kaolinite crystal. The total density of states of the kaolinite cluster are located near the Fermi level at both sides of the Fermi level. Both the highest occupied molecular orbit (HOMO) and the lowest unoccupied molecular orbit (LUMO) of kaolinite indicate that kaolinite system can not only readily interact with electron-acceptor species, but also readily interact with electron-donor species on the edge surface and the gibbsite layer surface, and thus, shows amphoteric behavior. Substitution of Al3+ for Si4+ in the tetrahedral site linking the vacant Al3+ octahedra does not increase the surface chemical reactivity of kaolinite, while substitution of Al3+ for Si4+ in the tetrahedral site with the apex O linking Al3+ octahedra increase the surface chemical reactivity of the siloxane surface of kaolinite, especially acting as electron donors. Additionally, substitution of Al3+ for Si4+ in the tetrahedral site results in the re-balance of charges, leading to the increase of negative charge of the coordinated O atoms of the AlO4 tetrahedra, and therefore favoring the formation of ionic bonds between cations and the surface O atoms in the basal plane.
Ansa-Cyclohexyl-bis(4,5,6,7-tertrahydro-1-indenyl) zirconium dichloride (5) was used as catalyst for propylene and ethylene polymerization together with methyl aluminoxane (MAO) as the cocatalyst. Isotactic polypropylene (PP) was obtained with the highest activity of 6.37×107g PP (molZr)−1h−1. The meso-meso (mmmmm) pentads sequence content of PP was determined by 13C NMR spectroscopy. The dependence of the microstructure on the reaction temperature and the Al/Zr molar ratio was examined and the catalytic activity of complex 5 was compared with that of the similar ansa-zirconocene 3. The high activity of the new zirconocene 5 for propylene isospectic polymerization at high temperature (60 °C) is the result of its unique bridged-group structure. Complex 5/MAO displays also high catalytic activity of 0.46×106 to 9.87×106g PE(molZr)−1h−1 in the homo-polymerization of ethylene. The visometric molecular weight of PE ranges from 0.97×104 to 11.16×104 g·mol−1 under the given conditions.13C NMR spectroscopy analysis proves the PE to be linear polyethylene (LPE).
ZnAb initio calculations on reactivity of tourmaline were performed using both Gaussian and density function theory discrete variation method (DFT-DVM). The HF, B3LYP methods and basis sets STO-3G(3d,3p),6-31G(3d,3p) and 6-311++G(3df,3pd) were used in the calculations. The experimental results show energy value obtained from B3LYP and 6-31++1G(3df,3pd) basis sets is more accurate than those from other methods. The highest occupied molecular orbital (HOMO) of the tourmaline cluster mainly consists of O atom of hydroxyl group with relative higher energy level, suggesting that chemical bond between those of electron acceptor and this site may readily form, indicating the higher reactivity of hydroxyl group. The lowest unoccupied molecular orbital (LUMO) of the tourmaline cluster are dominantly composed of Si, O of tetrahedron and Na with relative lower energy level, suggesting that these atoms may tend to form chemical bond with those of electron donor. The results also prove that the O atoms of the tourmaline cluster have stronger reactivity than other atoms.
The structure of bacterial cellulose (BC) produced by Acetobacter xylinum NUST4 (A.xylinum NUST4) under static (SBC) and shake culture condition (ABC) was studied by means of transmission electron microscopic (TEM), X-ray diffraction (XRD) and Fourier transform-infrared spectrum (FT-IR). It was revealed that BC is I crystal cellulose and the proportion of cellulose Iα exceeds 80% and BC diameter is 10–80 nm. Mechanical properties and water absorption capacity were also determined. These properties could result from crystalline and nanometer structure of BC.
A novel bioactive and bioresorbable asymmetry film was prepared. The PDLLA membrane was activated by 1, 6-hexanediamine to obtain a stable positive charge surface. Chondroitin sulfate and chitosan were then deposited on activated PDLLA membrane via layer-by-layer (LBL) electro-static assembly (ESA) technique. The deposition process was monitored by UV-Vis absorbance spectroscopy. The composite membrane was frozen lyophilized to form the asymmetry film and characterized by attenuated total reflection (ATR)-FT-IR, XPS and SEM. The experimental results show that a stable 1, 6-hexanediamine layer on PDLLA substrate based on the aminolysis of the polyester and the layer thickness increase linearly first with the increase of the deposited layers, and then increases slowly due to the layer interpenetration. The test results of ATR-FT-IR and SEM show the asymmetry film is modified uniformly with a dense inner layer and a porous sponge outer layer.
Porcine aortic valves were decellularized with trypsinase/EDTA and Triton-100. With the help of a coupling reagent Sulfo-LC-SPDP, the biological valve scaffolds were immobilized with one of RGD (arginine-glycine-aspartic acid) containing peptides, called GRGDSPC peptide. Myofibroblasts harvested from rats were seeded onto them. Based on the spectra of X-ray photoelectron spectroscopy, we could find conjugation of GRGDSPC peptide and the scaffolds. Cell count by both microscopy and MTT assay showed that myofibroblasts were easier to adhere to the modified scaffolds. It is proved that it is feasible to immobilize RGD peptides onto decellularized valve scaffolds, and effective to promote cell adhesion, which is beneficial for constructing tissue engineering heart valves in vitro.
PDLLA/CHI/β-TCP/NGF composite films were prepared by a solvent evaporation method. The degradation characteristics of the poly (d, l-lactide) composite films were studied in vitro and in vivo. The acidity produced by poly (d, l-lactide) materials was not obvious. Adding chitosan and β-TCP can relieve the acidity problem and improve strength performance of films. The NGF has influences on the degradation characteristics of films. It is verified that PDLLA/CHI/β-TCP/NGF composite films prepared by solvent evaporation method have excellent degradation characteristics. It can be used as a perfect biomaterial for repairing nerve injuries.
The cytotoxicity profile of three chitosan derivatives with different affinity to water was evaluated in vitro. The derivatives selected were carboxymethylated-chitosan (CMCH), linoleic acid modified-chitosan (LACH) and deoxycholic acid modified-chitosan (DACH), respectively, and the results of FTIR and NMR confirmed the successful modification. Cytotoxicity of these polymers was investigated via the red blood cell lysis assay and the MTT assay. The red blood cell lysis test showed that CH elicited a certain level of red blood cell toxicity, while CMCH, LACH and DACH all displayed low membrane damaging effects, with the hemolysis rates of 2.385%, 1.560% and 4.404%, respectively, which comes well within permissible limit (5%). The MTT assay revealed that CH exhibited significant inhibitory effect on fibroblast proliferation at higher concentration, while its three derivatives showed no cytotoxicity. CMCH had stimulatory effects on fetal mouse fibroblast proliferation. Differences in cytotoxicity of CH and its derivatives may result from the specific chemical modifications leading to the alteration of molecular charge density and type of the cationic functionalities, structure and sequence, and conformational flexibility.
To investigate the osteoinductive and ectopicly osteogenic effects of a novel peptide P24 derived from bone morphogenetic protein 2 (BMP2), biodegradable collagen scaffolds (CS) were used to load BMP-2-derived peptide solutions with different concentrations (0.4 mg peptide/CS, 0.1 mg peptide/CS and pure CS, respectively), and the implants were implanted into muscular pockets on the back of Wistar rats. Radiographs and histological analysis were performed to evaluate the ectopic bone effects. Active ectopic bone formation was seen in both groups containing the peptide at different concentration (0.4 mg and 0.1 mg), whereas no bone formation and only fibrous tissue was seen in the pure CS group. The new bone formation induced by the peptide P24 displayed a dose-dependent and time-dependent efficiency. The new bone formation in the 0.4 mg peptide/CS group significantly increased than that of the 0.1 mg peptide/CS group. This novel BMP-2-derived peptide had excellent osteoinductive and ectopicly osteogenic properties which were similar to those of BMP2.
Fe-Al intermetallic/TiC-Al2O3 ceramic composites were successfully prepared by self-propagating high-temperature synthesis (SHS) from natural ilmenite, aluminium and carbon as the raw materials. The effects of carbon sources, preheating time and heat treatment temperature on synthesis process and products were investigated in detail, and the reaction process of the FeTiO3-Al-C system was also discussed. It is shown that the temperature and velocity of the combustion wave are higher when graphite is used as the carbon source, which can reflect the effect of the carbon source structure on the combustion synthesis; Prolonging the preheating time or heat treatment temperature is beneficial to the formation of the ordered intermetallics; The temperature and velocity of the combustion wave are improved, but the disordered alloys are difficult to eliminate with the preheating time prolonged. The compound powders mainly containing ordered Fe3Al intermetallic can be prepared through heat treatment at 750 °C.
A new kind of composite piezoelectric ceramics for large-displacement actuators, which were composed of reduced and unreduced layers, was prepared from normal PZT by chemical reduction. The stress distribution inside the composite PZT was researched and the chemical reduction conditions were explored. The actuating properties of reduced PZT were also studied. It is found that the optimal ratio of reduced layer thickness for the composite structure is 0.3; Reduced composite PZT has lower resonance frequency and 3 times larger displacement than that of the traditional PZT; Re-oxide phases are found in reduced layer of composite PZT showing the reduction procedure needs to be improved.
Low-voltage electromagnetic compaction (EMC) was used to compact metal powders (Cu) and ceramic powders (TiO2) in the indirect way. It was found that the density of the metal powder parts compacted by low-voltage EMC varied linearly with the discharging voltage in the range investigated. But for ceramic powders, the discharging voltage has an optimal value. Under the value, the density increases as discharging voltage rises, but beyond the value the trend is reverse. The experimental results show that the density of the metal parts decreases gradually along press direction. And the density of the ceramic parts decreases with the advancement of the aspect ratio h/d (height /diameter). In addition, repetitive compaction can improve the density of both metal and ceramic parts and reduce the effects of aspect ratio on the density.
A novel method was used to fabricate AlN coating on graphite substrate. This approach included two steps: firstly, the emulsion composed of BN and anhydrous ethanol was sprayed on the surface of the graphite substrate; secondly, AlN coating was formed through the in-situ reaction of Al with the sprayed BN. The reaction was investigated by thermogravimetric-differential thermal analysis (TG-DTA), and the phase composition in the synthetic process was characterized by X-ray diffraction (XRD). Scanning electronic microscopy (SEM) was used to observe the morphology, and electron probe microanalysis (EPMA) was used to observe the distribution of the elements. The experimental results show that the AlN coating is dense and bonded with graphite tightly.
NaNbO3-Co2O3 co-added PZN-PZT (PZCNNT) ceramics were prepared using conventional solid state reaction. The piezoelectric and dielectric properties were measured. The experimental results show that the addition of 0.3mol% Co2O3 leads to low dielectric loss (tg δ) in PZCNNT ceramics and the proper addition of NaNbO3 not only improves piezoelectric properties but also decreases intensively dielectric loss and mechanical loss. The optimal ceramic having d 33=310 pC/N, k p=0.59, ɛ r=985, tg δ=0.0034, Q m=1380 was obtained.
Using the microwave sintering technology, the effects of phosphorus (P) additions on the microstructure and properties of the ultrafine WC-10Co alloys were investigated. The experimental results show that with only 0.3wt% P additions, full density WC-10Co cermets were obtained at temperature of 1250 °C, which is 70 °C lower than that of the undoped counterparts. Lower sintering temperature can result in finer WC grain growth; therefore, the P-doped WC-10Co alloys exhibited higher hardness than the undoped ones. But at the same time, P doping could lead to sacrifice of fracture toughness of WC-10Co cemented carbides.
The compressive strength and dynamic modulus of high volume fly ash concrete with incorporation of either metakaolin or silica fume were investigated. The water to cementitious materials ratio was kept at 0.4 for all mixtures. The use of high volume fly ash in concrete greatly reduces the strength and dynamic modulus during the first 28 days. The decreased properties during the short term of high volume fly ash concrete is effectively compensated by the incorporation of metakaolin or silica fume. The DTA results confirmed that metakaolin or silica fume increase the amount of the hydration products. An empirical relationship between dynamic modulus and compressive strength of concrete has been obtained. This relation provides a nondestructive evaluation for estimating the strength of concrete by use of the dynamic modulus.
The dynamic characteristics of fiber-modified asphalt mixture were investigated. Cellulose fiber, polyester fiber and mineral fiber were used as additives for asphalt mixture, and the dosage was 0.3%, 0.3%, 0.4%, respectively. Dynamic modulus test using SuperPave simple performance tester (SPT) was conducted to study the dynamic modulus (E*) and phase angle (δ) for the control asphalt mixture and fiber-modified ones at various temperatures and frequencies. Experimental results show that all fiber-modified asphalt mixtures have higher dynamic modulus compared with control mixture. The dynamic modulus master curves of each type of asphalt mixtures are determined based on nonlinear least square regression in accordance with the timetemperature superposition theory at a control temperature (21.1°C). The fatigue parameter E*×sinδ and rutting parameter E*/sinδ of asphalt mixture are adopted to study the fatigue and rutting-resistance properties, and experimental results indicate that such properties can be improved by fiber additives.
Chloride ion critical content was studied under soaking and cycle of dry and wet conditions, with three electrochemical nondestructive measuring techniques, i e, half-cell potential, A C impedance, and time potential. The experimental results show that chloride ion critical content is primarily determined by the water cement ratio, while for the same concrete mixture the chloride ion critical content in soaking conditions is larger than that in a cycle of dry and wet conditions.
A new kind of mortar made of ground granulated blast-furnace slag (GGBFS), gypsum, clinker and steel slag sand (<4.75 mm) was developed. The ratio of steel slag sand to GGBFS was 1:1 and the amount of gypsum was 4% by weight while the dosage of clinker ranged from 0% to 24%. The optimization formulation of such mortar was studied. The content of steel slag sand should be less than 50% according to the volume stability of blended mortar, and the dosage of clinker is about 10% based on the strength development. Besides strength, the hydration heat, pore structure and micro pattern of blended mortar were also determined. The experimental results show the application of steel slag sand may reduce the dosage of cement clinker and increase the content of industrial waste product such as GGBFS, and the clinker is also a better admixture for blended mortar using steel slag sand.
The chemical composition and mineral structure of fluorgypsum as well as its harm to application in cement were elaborately analyzed. The primary fluorgypsum was modified and its applications in cement’s production were studied. The technological flow chart of preparing modified fluorgypsum was given. Experimental results indicate that hydration ratio the modified fluorgypsum through adding compound additive for 14d is about 70%. The modified fluorgypsum as cement retarder has certain stimulation to fly ash and increases the strength of compound cement. In addition, its adding amount is lower than that of natural gypsum. The modified fluorgypsum is a good substitute for natural gypsum.
Coal gangue was activated by means of calcination in seven temperature ranges. Systematic research was made about activation mechanism and structural evolution. Glycerin-ethanol method, SEM, MIP and XRD were used to determine the variation of structure and activation of coal gangue during the calcination. The experimental results show that because of heat treatment in the range of calcination temperature, mineral composition and microstructure of coal gangue are changed. In addition, its activity is improved evidently. The amount of lime absorbed by the sample calcined at 700 °C is 2–4 times that by uncalcined coal gangue in the course of hydration. When NaOH is added to coal gangue-lime system, hydration reaction of the system is sped up and the microstructure of hydrating samples of coal gangue is improved.
To study the surface modification of SiC powders with aminoorganosilanes, high solid loading and low viscosity SiC slurry was prepared. Three kinds of aminoorganosilanes were used in the experiment. Infrared Fourier transform spectrometry (Nicolet20SX, America) was applied to analyze the surface characterization of modified SiC powders. The largest solid loading of SiC coated with WD-52 slurry had increased to 54.5vol% and the stabilization also increased remarkably. At the same time, the viscosity of SiC slurry declined. Comparing with WD-50 and WD-57, WD-52 is most effective for modification of SiC powders.
The auto efficiently hydration heat arrangement and the non-contacting electrical resistivity device were used to test the thermology effect and the resistivity variation of Portland cement hydration. The structure forming model of Portland cement initial hydration was established through the systematical experiments with different cements, the amount of mixing water and the chemical admixture. The experimental results show that, the structure forming model of cement could be divided into three stages, i e, solution-solution equilibrium period, structure forming period and structure stabilizing period. Along with the increase of mixing water, the time of inflexion appeared is in advance for thermal process of cement hydration and worsened for the structure forming process. Comparison with the control specimen, adding Na2SO4 makes the minimum critical point lower, the flattening period shorter and the growing slope after stage one steeper. So the hydration and structure forming process of Portland cement could be described more exactly by applying the thermal model and the structure-forming model.
The samples were attained through altering the cooling system of producing glass-ceramics. The X-ray diffraction was used to test the stress value of different samples. The relation of the cooling system and internal stress were also investigated. The experimental results show that the stress of glass-ceramic had a close relation with starting cool temperature. Above 800 °C, glass-ceramic could be accelerated cooling and did not bring stress. Temperature between 500 °C and 800°C was an important temperature range of the formation of stress in glass-ceramic, in which the glass-ceramic stress would change obviously. Cool system was the key on how to control and eliminate internal stress in order to reduce the destroy of materials crated by internal stress. In addition, glass particles size increase, glass-ceramic stress increase in consequent.
The half cell potential (HCP) and corrosion current of reinforced concrete specimens doped with sodium chloride were determined after electrochemical chloride extraction (ECE). The experimental results show that when ECE treatment is removed, HCP becomes more negative and corrosion current becomes larger in comparison to those before ECE treatment, then HCP shifts positively and corrosion current decreases with time. After 30 days ECE treatment, the HCP of cored specimens turn to about −100 mV due to the existence of sufficient oxygen around the exposed steel bars, but for un-cored specimens, longer time, about two months, is to be taken. The non-homogeneous HCP distribution at different layers of the same specimen after ECE treatment might induce secondary corrosion of steels.
The slice-weighing method was used to investigate the unsaturated water transport of different cement pastes. The experimental results show that a sharp wetting front existed during water transport, the transport can be described by a non-linear diffusion equation, and transport coefficient of different materials exhibit various rules with water content of materials. The addition of fly-ash decreases transport coefficient of cement pastes in all the various water contents, even changes the transport mechanism.
The dielectric performance of alkali activated slag (AAS) cement paste was investigated in the frequency range of 1 to 1000 MHz. The experimental results showed the unstable dielectric properties of harden paste were mostly influenced by the fraction of free water in paste or absorbed water from ambient, but not including hydration water and microstructure. The free water was completely eliminated by heat treatment at 105 °C about 4 hours, and then its dielectric loss was depressed; but with the exposure time in air increasing, the free water adsorption in ambient air made the dielectric property of harden cement paste to be bad. The temperature and relative humidity of environment was the key factors of free water adsorption; hence, if the influence of free water on dielectric constant was measured or eliminated, the cement-based materials may be applied in humidity sensitive materials or dielectric materials domains.