bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and Dielectric Properties of Rare Earth (Y, Ho) Doped Ba0.95Ca0.05Ti0.85Zr0.15O3 Ceramics
Authors: Shen Zheng Bo , Wang Xiao Hui , Gong Hui Ling , Li Long Tu
Published: March 2014

Ba0.95Ca0.05Ti0.85Zr0.15O3(BCTZ) dielectric ceramics were fabricated by traditional solid-state method, using barium carbonate, calcium carbonate, titanium dioxide and zirconium dioxide as the starting materials. Rare earth dopants have a significant influence on the dielectric properties of BCTZ ceramics. The doping effects of Y and Ho with different content on the dielectric properties and structure were studied respectively. The results reveal that the effects of Y and Ho are similar, they perfer to occpy B site, and they move the dielectric peak to lower temperature, widen the peak and increase the insulation resistivity, thus improve the dielectric properties obviously. The effects were investigated by X-ray diffraction, scanning electron microscope, and dielectric property measurements. After rare earth elements-doping, the BCTZ ceramics satify the Y5V EIA specifications, mainly due to the change of structure. The BCTZ dielectric ceramics with high permittivity over 10,000, high insulation resistivity over 1012Ωcm, low dielectric loss less than 1%, can be applied in multilayer ceramic capacitors (MLCCs).
Effect of Sintering Behaviors on Microwave Dielectric Properties of (Ca0.3Sr0.1)Sm0.4TiO3 Ceramics
Authors: Hsu Cheng Hsing , Tsai Shang Hung , Chen Wen Shiush , Lai Chun Hung , Lin Jenn Sen
Published: March 2014

The microstructure and dielectric properties of the (Ca0.3Sr0.1)Sm0.4TiO3 ceramics with various sintering conditions have been investigated. The compounds were prepared by the conventional solid-state route with various sintering temperatures from 1340 to 1400°C and sintering duration from 3 h. The resultant microwave dielectric properties were analyzed based upon the densification, the X-ray diffraction patterns and the microstructures of the ceramics. The correlation between the microstructures, the microwave dielectric properties and sintering behaviors was also examined. The εr value of 96.7 and Q×f value of 11,600 GHz were obtained for (Ca0.3Sr0.1)Sm0.4TiO3 ceramics sintering at 1370°C for 3 h. The (Ca0.3Sr0.1)Sm0.4TiO3 ceramics had suitable dielectric properties can find applications in microwave devices such as resonator, filter and antenna.
Phase-Structure Transformation in Low-Si/Al-Ratio Geopolymers
Authors: Wang Yi Pin , He Yan , Liu Jing , Cui Xue Min
Published: March 2014

To obtain low-Si/Al-ratio geopolymers and overcome the disadvantage of impure raw materials, amorphous Al2O3-SiO2 powder was first prepared using a sol-gel method in accordance with specially designed chemical compositions. The composition of the geopolymers was designed according to the NaA zeolite composition (Si/Al/Na atom ratio is 1:1:1), and the zeolite crystal structure was obtained by geopolymers with high Na/Al ratios through hydrothermal processing at 90oC for 6 h. The geopolymers with Si/Al ratios ranging from 0.9 to 1.05 exhibited amorphous structures after being cured at 60oC for 24 h; however, the geopolymer sample with a Si/Al ratio of 1.1 exhibited crystallization. After the hydrothermal treatment of these geopolymers , the XRD, SEM and NMR results show that the phase structure of the geopolymers may transform into a crystalline structure under appropriate compositions and external conditions. Hence, the alkalinity, Si/Al ratio and hydrothermal conditions determined the crystallinity of the geopolymers that were synthesized.
Preparation and Electromagnetic Wave Absorption Properties of Core-Shell Ni/TiO2 Microspheres
Authors: Zhao Biao , Fan Bing Bing , Chen Hao , Pian Xiao Xuan , Wang Bin Bin , Li Wen , Sun Bing , Wang Chen Yang , Zhang Rui
Published: March 2014

The composite microspheres with Ni cores and amorphous TiO2 shells (Ni@TiO2) were synthesized by a one-pot solvothermal method at 180°C for 15 h, which used nickel chloride hexahydrate as Ni source andtetrabutyl orthotitanate as Ti source. The Ni/TiO2 core/shell composites were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX). A possible formation mechanism of core-shell Ni/TiO2 was proposed. Furthermore, the microwave absorption properties of these microspheres were investigated in terms of complex permittivity and permeability. The minimum reflection loss is-29.5 dB at 14.4 GHz for a layer of 4.0 mm thickness. Such phenomenon is attributed to the synergy effect between magnetic loss of Ni core and dielectric loss of amorphous TiO2 shell. The enhanced microwave absorption properties are also believed to be due to the unique coreshell structure. All results indicate that these Ni@TiO2 microspheres may be attractive candidate materials for electromagnetic wave absorption applications.
Effect of Y2O3 on Phase Transformation and Dielectric Properties of Alumina Ceramics
Authors: Qian Fen Ling , Xie Zhi Peng , He Zhi Yong , Zhang Qi Fu
Published: March 2014

Alumina ceramics can be widely used in electro vacuum area and microwave communication industry due to its excellent dielectric properties. However, the effects of the Y2O3addition on dielectric properties of alumina ceramics were rarely investigated. In this paper, alumina ceramics was prepared using Y2O3as additive, via both heterogeneous precipitation method (HP) and mechanical milling method (MM). The effect of Y2O3on phase transformation during sintering and dielectric properties of alumina ceramics were investigated, and the influencing mechanism was discussed. The results showed that different adding way influenced phase transformation during sintering, and polarization relaxation existed in alumina ceramics during 103~107Hz. Besides, the universal polarization relaxation relation could be applied to alumina ceramics.
Low-Temperature Sintering and Enhanced Piezoelectric Properties in KNN-LTS Nanopowder Prepared via a Low-Cost Water-Based Sol-Gel Method
Authors: Huan Yu , Wang Xiao Hui , Li Long Tu
Published: March 2014

nanoscale lead-free perovskite powders with a composition of (Na0.52K0.4425Li0.0375)(Nb0.9125Ta0.0375Sb0.05)O3 (KNN-LTS) have been synthesized via a low-cost water-based sol-gel method, to reduce the sintering temperature and enhance the electrical properties. KNN-LTS nanopowders with average particle size of about 20 nm are obtained by citrate precursor sol-gel process, where Nb (OH)5 and Sb2O3 are used to replace the costly mental alkoxides. The sol-gel derived nanopowders can be densified at lower temperature of 940 °C and exhibited excellent electrical properties after sintering at 1020 °C (d33 = 396 pC/N, kp = 50.1% = 1882 and tanδ = 0.02), providing a tremendous potential method for high-performance lead-free ceramics preparation.
Electrical and Physical Properties of (K0.5Na0.5)NbO3 Ferroelectric Thin Films
Authors: Kuan Min Chang , Yang Fann Wei , Cheng Chien Min , Chen Kai Huang , Lee Jian Tz
Published: March 2014

Lead-free potassium sodium niobate ceramic thin films were synthesized using rf magnetron sputtering technology for MFIS structures. The optimal sputtering parameters of the as-deposited KNN thin films for depositing times of 1h were obtained. Regarding the measured physical properties, the micro-structure and thickness of as-deposited KNN thin films for different oxygen concentration were obtained and compared by XRD patterns and SEM images. The surface roughness of KNN thin film was also observed by AFM morphology. The average grain size and root mean square roughness were 250 and 7.04 nm, respectively.
For KNN thin films in the MFIS structure, the capacitance and leakage current density were 280 pF and 10-8A/cm2, respectively. We investigated that the leakage current density and the memory window increased, the capacitance critically increased as the oxygen concentration increased from 0 to 40%. However, the excess oxygen concentration process was decreased the electrical and physical of as-deposited KNN thin film. The effect of oxygen concentration on the physical and electrical characteristics of KNN thin films was investigated and determined.
Microstructure and Electrical Properties of Y2O3 and Sb2O3 Co-Doped ZnO-Based Varistors
Authors: Fu Xiu Li , Zang Yan Xu , Peng Zhi Jian
Published: March 2014

Through a conventional ceramic process, Y2O3 and Sb2O3 co-doped ZnO-based varistors were prepared. The microstructure and electrical properties of the as-prepared varistors were investigated. Y2O3 could act as an inhibitor to the growth of ZnO grains when working with Sb2O3. The mean size of ZnO grains in the Sb2O3 and Y2O3 co-doped samples was smaller than those of the samples only added with Y2O3 or Sb2O3. And with appropriately increased ratio of Y:Sb, it would result in increased sample densification. When the doping level of Y2O3 was small, the nonlinear coefficientand breakdown voltage of the varistors would increase with increasing doping amounts of Y2O3, and the leakage current would decrease. However, when Y2O3 was doped without Sb2O3, both the nonlinear coefficientand breakdown voltage of the varistors would decrease sharply, thus the leakage current increase dramatically. The electrical properties of the Sb2O3 and Y2O3 co-doped varistors would be better than those of the samples only added with Y2O3 or Sb2O3, and when the Y:Sb atom ratio was 5, the nonlinear coefficients, breakdown voltages and leakage current of the varistors reached their optimum values of 777 V/mm, 23 and 0.17 mA/cm2, respectively.
Effect of La2O3 Concentration on Electrical Properties of Barium Strontium Titanate Glass-Ceramics
Authors: Zhu Jia , Zhang Yong , Tian Wei , Song Xiao Zhen , Zhang Qian
Published: March 2014

Barium strontium titanate glass-ceramics with different La2O3 concentrations have been prepared by a melting-annealing technique. The effect of La2O3 concentration on phase evolution, microstructure and electrical properties of (Ba,Sr)TiO3-Al2O3-SiO2 glass-ceramics has been investigated. The X-ray diffraction results showed the volume fraction of the major perovskite (Ba,Sr)TiO3 crystalline phase increased with increasing La2O3 concentration. In addition, the scanning electron microscopy observations revealed that small amounts of La2O3 could accelerate the growth of crystals. When the La2O3 concentration was increased to 1.5 mol%, the microstructure of these samples displayed nonuniform distribution of the crystals. The dc conductivity measurements showed an increasing temperature dependence of conductivity with La2O3 doping at high temperature range above 400 °C. Impedance spectroscopy analysis indicated that the additive of La2O3 changed the major polarization mechanism to the relaxation polarization and the relaxation time for the La2O3 doped samples was much shorter than the undoped ones. The frequency dependence of dissipation factor curve displayed a peak at the range of 1 to 10 kHz due to the La2O3 addition. And the peak value decreased with increasing La2O3 concentration.
LSGM-Carbonate Composite Electrolytes for Intermediate-Temperate SOFCs
Authors: Zhong Hai Tao , Ai De Sheng , Lin Xu Ping
Published: March 2014

LSGM(La0.9Sr0.1Ga0.8Mg0.2O3-δ)-carbonate composite electrolyte was prepared by molten salt infiltration method and its properties were analyzed by scanning electron microscope (SEM), X ray diffractometer (XRD) and A.C. impedance. LSGM-carbonate composite electrolyte showed the same phase patterns as pure LSGM which suggests carbonates exist in an amorphous state. SEM images of porous LSGM pellet indicated all of the pores are uniformly distributed and nearly all of them are connected with each other. The A.C conductivity measurements showed composite electrolyte possessed a much higher ionic conductivity than LSGM electrolyte at a temperature within the range of 450-650 oC. Conductive highways for oxygen ions and multi-ions conduction were employed in explaining the improved property of composite electrolyte.
Characteristics of Zinc Oxide Film Prepared by Chemical Bath Deposition Method
Authors: Fu Yen Pei , Chen Jian Jhih
Published: March 2014

In this study, ZnO films, prepared by Chemical Bath Deposition (CBD), are applied as the conductive layers for thin film solar cells. Zinc acetate is used as a source of zinc, and different proportions of ammonia solution are added and well mixed. The growth of zinc oxide films in reaction solutions is taken place at 80°C and then heated to 500°C for one hour. In this study, the different ammonia concentrations and deposition times is controlled. The thin film structure is Hexagonal structure, which is determined by X-ray diffraction spectrometer (XRD) analysis. Scanning electron microscopy (SEM) is used as the observation of surface morphology, the bottom of the film is the interface where the heterogeneous nucleation happens. With the increase of deposition time, there were a few attached zinc oxide particles, which is formed by homogeneous nucleation. According to UV / visible light (UV / Vis) absorption spectrometer transmittance measurements and the relationship between/among the incident wavelength, it can be converted to the energy gaps (Eg), which are about 3.0 to 3.2eV, by using fluorescence spectroscopy analysis. The emission of zinc oxide films has two wavelengths which are located on 510nm and 570nm. According to Based on the all analytic results, the ammonia concentration at 0.05M, and the deposition time is 120 minutes, would obtain the conditions of ZnO films which is more suitable for applications of conductive layer material in thin film solar cell.
Synthesis and Characterization of SnO2 Nano-Cystalline for Dye Sensitized Solar Cells
Authors: Song J.G. , Hua Lin , Shen Qiang , Wang Fang , Zhang Lian Meng
Published: March 2014

The study of dye-sensitized solar cells (DSCs) based on nanocrystalline films of high band gap semiconductors is a progressive field of research that is being carried out by scientists in a wide range of laboratories. Of the many semiconductor materials utilized for conversion of solar energy into electricity, SnO2 is a high band gap semiconductor that has been used extensively. However, its efficiency is at a relatively lower level when compared to other semiconductor materials such as TiO2 working under similar circumstances. To improve the conversion efficiency of the DSCs, the SnO2 nanorots photocurrent is prepared via the hydrothermal method, and characterized by XRD, FESEM, BET and Absorption spectrum. Though analysis the results, SnO2 nanocrystalline were successfully synthesized using a hydrothermal method by certainly experimental parameters. The SnO2 nanocrystalline is the rod-shape with length for 100nm and diameter for 5nm as pH=11. the specific surface area is 86.3412m2/g, which lay base for reaching the high conversion efficiency of the DSCs.
Preparation of α-Al2O3 Powder by Microwave Pyrolysis
Authors: Chen Hao , Fan Bing Bing , Zhang Xin , Pian Xiao Xuan , Zhang Rui
Published: March 2014

A fast method of microwave pyrolysis was provided to prepare α-Al2O3 powders. Aluminum hydroxide and Aluminum ammonium sulfate doclecahydrate were used as raw materials to obtain α-aluminum oxide powder by microwave pyrolysis, respectively. Thermo-Gravimetric/Differential Thermal Analyzer (TG/DTA) and X-ray Diffraction (XRD) analysis were employed to investigate pyrolysis process and the transformation of metastables Al2O3 in the process of heating different precursors. Meanwhile, Flied Emission Scanning Electron Microscopy (FESEM) was applied to observe microstructure and grain growth, and the phase composition was characterized by XRD. The results indicated that the high purity α-Al2O3 was obtained which met the demands of market, and the sample obtained from aluminum hydroxide performed high purity, small particle size and, while the sample from ammonium aluminum sulfate showed lower purity and larger grain size.
Electrochemical Properties of xLiFePO4·yLi3V2(PO4)3/C Nanosized Composite Cathode Materials Prepared by Solid Reaction Method
Authors: Wang Ling , Gao Peng Zhao , Li Dong Yun , Tian Guang Lei
Published: March 2014

In this paper, a series of xLiFePO4·yLi3V2(PO4)3/C (x/y = 1:0, 7:1, 5:1, 3:1, 1:1, 1:3 and 0:1, ratio of mol) nanosized composite cathode materials were prepared by solid reaction method. Influence of x/y ratio on the composition, microstructure and electrochemical properties of the materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical measurements, et al. XRD patterns showed that most of iron (Fe) and vanadium (V) in raw materials tended to form the LiFePO4 and Li3V2(PO4)3 phases, while small amounts of them were as the dopant and entered into the lattice of Li3V2(PO4)3 and LiFePO4, respectively. TEM images exhibited that the 7LiFePO4·Li3V2(PO4)3/C composite shows good dispersion and the size ranging in 50-150 nm, which was coated uniformly with the carbon layer. The value of the first discharge specific capacity of the composites was 145.6 mAh/g and its capacity retention was 99.8% after 50 cycles at 0.1 C. Compared with the single LiFePO4 and Li3V2(PO4)3, its cycle performance was also remarkable improved.
Effect of Sr Doping on Structure and Emittance of La1-xSrxMnO3 Smart Thermal Control Films
Authors: Shen Yong Jun , Wang Chuan Bin , Li Ling , Shen Qiang , Zhang Lian Meng
Published: March 2014

Sr-doped lanthanum manganite (La1-xSrxMnO3) is characteristic of thermochromic, which can act as a smart thermal control material used in the variable-emittance devices. In the present study, La1-xSrxMnO3 thin films were prepared on MgO(100) substrates by pulsed laser deposition, and the effect of Sr-doping (x = 0 ~ 0.4) on the structure and infrared emissivity was investigated. Single-phased La1-xSrxMnO3 films with (100)-orientation were obtained, which showed a dense texture with smooth surface. The ratio of Mn4+/Mn3+ in the films was increased with increasing Sr doping, leading to the enhancement in double-exchange interaction and electrical conductivity. As a result, the phase transition from metal to insulator was observed with the increasing of test temperature. For the La0.8Sr0.2MnO3 thin film, a large value of emittance (De = 0.28) was obtained, indicating good variable-emittance by appropriate Sr doping.
Thermoelectric Properties of Ni Doped P-Type BiCuSeO Oxyselenides
Authors: Liu Yao Chun , Liu Jun Fu , Zhang Bo Ping , Lin Yuan Hua
Published: March 2014

We report on the effect of Ni doping on the thermoelectric properties of p-type BiCuSeO oxyselenide, with layer structure composed of conductive (Cu2Se2)2-layers alternately stacked with insulating (Bi2O2)2+layers along c axis. After doping with Ni, enhanced electrical conductivity coupled with a moderate Seebeck coefficient leads to a power factor of ~231 μwm-1K-2at 873 K. Coupled to low thermal conductivity, ZT at 873 K is increased from 0.35 for pristine BiCuSeO to 0.39 for Bi0.95Ni0.05CuSeO. However, the efficiency of Ni doping in the insulating (Bi2O2)2+layer is low, and this doping only leads to a limited increase of the hole carriers concentration. Therefore Ni doped BiCuSeO has relatively low electrical conductivity which makes its thermoelectric figure of merit much lower than that of Ca, Sr, Ba and Pb doped BiCuSeO.
Enhancement of Energy Storage Properties in PLZST Cramics with Different Zr/Sn Ratios
Authors: Zhang Qian , Zhang Yong , Liu Xiao Lin , Song Xiao Zhen , Zhu Jia
Published: March 2014

The effect of Zr/Sn ratio on the dielectric and energy storage properties of lanthanum modified lead zirconate stannate titanate (PLZST) ceramics with compositions located near the boundary between antiferroelectric and ferroelectric phases was studied. Microstructural observation indicated that all the samples had a uniform morphology with pure perovskite phase and the average grain size reduced obviously with increasing Zr/Sn ratio. As the Zr/Sn ratio increased, the dielectric constant increased and the transition temperature Tm shifted to higher temperature. All the PLZST ceramics exhibited double hysteresis loops. The maximum polarization increased, while the switching field decreased when the Zr/Sn ratio increased. The variations of Zr/Sn ratio had little impact on remanent polarization. As a result, both charged energy density and discharged energy density increased with increasing Zr/Sn ratio. A high energy storage density of 1.75 J/cm3 was achieved in the PLZST ceramics with the Zr/Sn ratio of 82.5/7.5 at 9 kV/mm.
Non-Covalent Functionalization of Graphene and Multiwalled Carbon Nanotubes Composites for Transparent Conductive Films
Authors: Zhao Chun Lin , Xing Li , Xiang Jun Hui , Sai Hua Zheng , Li Zhen You , Li Fei
Published: March 2014

In this paper, dry ice is converted into few-layer graphene, which can be dispersed stably in N, N-Dimethylformamide (DMF) by adding pyrene-1-boronic as a stabilizer that non-covalently functionalizes the surface of graphene to obtain homogeneous colloidal suspensions. Moreover, we make use of vacuum filtration transferring for fabricating transparent conducting graphene films by incorporating multiwalled carbon nanotubes (MWNTs). The increased conductivity is ascribed to the formation of a more efficient network. Here a transmittance of 81% at 550 nm and a sheet resistance as low as 38.17 KΩ/sq are obtained.
Mössbauer Spectroscopy and Magnetoelectric Effect Studies of Multiferroic Ceramics Based on BiFeO3
Authors: Jartych Elzbieta , Pikula Tomasz , Kowal Karol , Lisińska-Czekaj Agata , Czekaj Dionizy
Published: March 2014

In this work the results of investigations for (BiFeO3)x(BaTiO3)1-xand Bi1-xNdxFeO3solid solutions are described. Samples were prepared by the conventional solid-state sintering method. X-ray diffraction,57Fe Mössbauer spectroscopy, and magnetoelectric effect measurements were applied as complementary methods to determine the structure and magnetic properties of materials. For (BiFeO3)x(BaTiO3)1-xsolid solutions Mössbauer spectroscopy revealed the relationship between the content of BiFeO3and the magnetic properties of the samples. Moreover, the presence of magnetoelectric coupling in (BiFeO3)x(BaTiO3)1-xsolid solutions was registered at room temperature for the materials sintered at various temperatures. The maximum value of magnetoelectric voltage coefficient was achieved for 0.7(BiFeO3)0.3(BaTiO3) sintered at 1153K. Structure of Bi1-xNdxFeO3solid solutions was investigated in the whole range of concentration. Hyperfine interactions parameters were determined for the first time for these solid solutions.
Crystal Structure of BiFeO3 Synthesized Using the Hydrothermal Processing
Authors: Wang Zhen , Chen Hai Yan , Gao Lin Qiang , Zou Xin
Published: March 2014

BiFeO3 nanoparticles were successfully synthesized by a hydrothermal method by a mineralizer (KNO3). Structural characterization was performed by thermal analysis, powder X-ray diffraction (XRD) and scanning electron microscopy (TEM).The results showed that the products were perovskite structure BiFeO3 powders. Optimal conditions for the synthesis of single-phase BiFeO3 ceramics were obtained.
Properties of ZnS Films Deposited by Radio Frequency Magnetron Sputtering
Authors: Zhang Lei , Huang Jian , Yang Hui Min , Tang Ke , Lin Mei Ai , Ren Bing , Zhang Kai Xun , Wang Lin Jun
Published: March 2014

In this work, zinc sulfide (ZnS) thin films were prepared by radio frequency (RF) magnetron sputtering on glass substrates. The effects of sputtering power, working pressure, substrate temperature and annealing treatment on the structural and optical properties of ZnS films were studied using X-ray diffraction and UV-visible spectrometer in detailed.
Preparation and Characterization of Nanocrystalline CaO-ZrO2 Powders by Microwave Pyrolysis
Authors: Fan Bing Bing , Guan Ke Ke , Chen Hao , Pian Xiao Xuan , Wang Chen Yang , Mao Qian Nan , Miao Li Na , Tong Fang Lei , Wu Hao
Published: March 2014

CaO(15%)-ZrO2nano-powders were prepared by microwave pyrolysis in a multi-model chamber at the temperature ranging from 650°C to 800°C, with the precursor processed at different reaction temperature from 0°C to 80°C by chemical co-precipitation method. XRD and SEM techniques were used to characterize the phase transition and micrograph of powders. It is found that the content of m-ZrO2phase decreased with the increasing of reaction temperature and pyrolysis temperature. The high dispersed and superfine nano-powders were obtained at the pyrolysis temperature of 750°C for 20 min at 80°C. And only cubic ZrO2phase were detected in CaO (15%)-ZrO2powders and the average size of the powders is about 41 nm.
Enhanced Photocatalytic Performance of Oriented ZnWO4 Nanorods via Graphene Hybridization
Authors: Zhou Feng , Zhan Su
Published: March 2014

The hybridization of graphene with oriented ZnWO4photocatalysts effectively enhanced the photocatalytic activity. The enhancement in photocatalytic performance was relied on the amount of graphene and the optimal hybridized amount of graphene was about 2 wt%. The photocatalytic activity was increased by about 3 times after ZnWO4was hybridized with graphene under UV irradiation. The enhancement mechanism of the photocatalytic activity is attributed to the higher separation efficiency and the inhibition of recombination of photoinduced electron-hole pairs.
Light-Emitting Characterization of Vacuum Plasma Sprayed Silicon Coatings
Authors: Niu Ya Ran , Zheng Xue Bin , Liu Xuan Yong , Ji Heng , Ding Chuan Xian
Published: March 2014

In the present work, the light-emitting property of silicon coating was explored and the related morphologies and chemical structure of silicon coating were characterized. Silicon coating was prepared by vacuum plasma spray technique and chemically treated by HNO3/HF vapor. The coatings before and after the vapor etching were characterized by field emission scanning electron microscopy and micro-raman spectroscopy. The photoluminescence spectra of the silicon coatings treated with different time were examined. It is found that pores of micrometer and microcracks formed on the surface of silicon coatings after the treatment. The treated silicon coatings exhibited room temperature visible photoluminescence with emission wavelength around 650 nm after excitation. The results of micro-raman measurement proved that there were polysilane and oxygen related functional groups appeared on the coating surface after the vapor treatment, which was supposed to be responsible for the photoluminescent phenomena.
Effect of Siliceous Pozzolanic Additives on the Hydration Process of Cement
Authors: Setina Janina , Gabrene Alona , Juhnevica Inna , Ose Ieva
Published: March 2014

The given study investigates the influence of pozzolanic admixtures both micro- and nanosize silica and biomass ashes on microstructure and properties of hydration process of cement paste. The investigations were carried out by - XRD, SEM and FTIR.
Pozzolanic activity of the concrete admixtures strongly depends on their chemical composition, content of reactive silica as well as the specific surface area.
The micro- and nanosilica pozzolanic additives demonstrated the higher values of pozzolanic activity. Those activate the process of mineralization and are acting both as the cementitious admixture as well as the fine filler.
Investigation of Morphology Changes on Nanocrystalline Diamond Film Surfaces during Reciprocating Sliding against Si3N4 Balls
Authors: Bogatov Andrei , Podgursky Vitali , Raadik Taavi , Kamjula Amarnath Reddy , Hantschel Thomas , Tsigkourakos Menelaos , Kulu Priit
Published: March 2014

This paper investigates the morphological modifications of the nanocrystalline diamond (NCD) film surface under reciprocating sliding test conditions. The surface morphology was characterized by atomic force microscopy (AFM). We observed longitudinal grooves and transverse ripples which were formed during the sliding tests on the NCD film surface. The primary goal of the study was to understand the influence of frequency, sliding distance and load variations on the formation of ripple patterns on the wear scars surface. The morphological alteration from continuous to broken ripple shapes was observed. Our study suggests that the geometrical shape of ripples is affected by the formation of the periodic array of grooves.
New Thermoshrinkable Materials of Radiation Modified Polypropylene-Elastomer Composites with Cross-Linking Agents
Authors: Reinholds Ingars , Kalkis Valdis , Zicans Janis , Merijs Meri Remo , Bockovs Ivans
Published: March 2014

In this work, electron beam modified heterogeneous composites of isotactic polypropylene (PP) with chlorinated polyethylene (CPE) have been investigated. The PP/CPE blend composites with an excess of elastomer (30/70 wt%) have been modified with trimethylolpropane triacrylate (TMPTA) and bisphenol-A-dimethacrylate (BPDMA) cross-linking agents and have been irradiated with accelerated electrons up to ionizing radiation doses from 25 to 150 kGy. The internal stresses characterizing the thermoshrinkage properties (TMP) thermorelaxation stresses formed in thermal heating and the residual stresses resulting in the process of full setting and cooling of materials have been investigated for radiation cross-linked oriented (extended up to 100%) composite samples. The dependence of cross-linking efficiency and the TMP characteristics of PP/CPE heterogeneous blends have been compared to properties of a low density polyethylene (LDPE), which has been commonly used as thermoshrinkable material (TSM) in polymer industry. It has been proved that the radiation-chemically modified PP multiphase composites with elastomers and the crosslinking promoters are comparable perspective materials for creation thermoshrinkable materials with higher or similar thermoshrinkage properties compared to currently exploited TSM.
Selective Oxidation of Glycerol to Glyceraldehyde over Novel Monometallic Platinum Catalysts
Authors: Chornaja Svetlana , Sproge Elina , Dubencovs Konstantins , Kulikova Lidija , Serga Vera , Cvetkovs Antons , Kampars Valdis
Published: March 2014

Several novel monometallic platinum catalysts supported on metal oxides (Al2O3, Y2O3, γ-Al2O3, Lu2O3, ZrO2-Y2O3 TiO2, SiO2, γ-AlO(OH)) and activated carbon (C) were synthesized by extractive-pyrolytic method and tested in glycerol oxidation processes without base addition to obtain glyceraldehyde. It was found that Pt catalyst activity is strongly influenced by support nature, oxygen partial pressure and Pt loading. Pt/Al2O3 and Pt/SiO2 catalysts exhibited the highest activity but selectivity to glyceraldehyde significantly decreased when glycerol conversion increased.
Anisotropy of Compressive Strength in Porous Alumina Ceramics
Authors: Zake-Tiluga Ieva , Svinka Ruta , Svinka Visvaldis
Published: March 2014

Anisotropy of the compressive strength was investigated in porous alumina based ceramics produced by slip casting method. Aluminium paste was used as pore former similarly as in the aerated concrete technology. Materials were sintered at 1650°C and 1750°C. The apparent porosity of the investigated materials was in the range of 54±1% to 60±2%. The compressive strength of the samples in the directions parallel and perpendicular to the sample expansion direction was in the range from 3.8±0.3 to 13.0±1.1 MPa and from 6.4±1.3 to 27.0±1.1 MPa, respectively. The mechanical anisotropy was related with the flattening of the introduced pores. The level of mechanical anisotropy was affected by the initial composition of the slurry and sintering temperature.
Reactive Spark Plasma Sintering of B-C-Ti-N Powders
Authors: Grabis Janis , Steins Ints , Patmalnieks Aloizijs , Sipola Inta
Published: March 2014

The TiB2-TiN0.1 C0.9 and B4C-TiB2 composites with relative density of 95.7-98.6% were manufactured by SPS reactive sintering mixtures of amorphous boron with TiN or TiNC and carbon nanoparticles at 1700 °C and pressure of 30 MPa during 10 min. The phase composition of the materials was determined in dependence on molar ratio of Ti/B and B/C.
Biodegradable Flax Fiber Reinforced Eco-Composites
Authors: Tupureina Velta , Dzene Anda , Dzenis Marcis
Published: March 2014

Formation process of flax fiber reinforced biocomposites based on waterborne matrix systems from modified polymers - polyhydroxybutyrate, poly (vinyl alcohol) was developed by suspension casting technique. Two kind of flax fiber as reinforcement was employed Latvian variety Vega-2 and flax combing. The correlation between matrix composition, fiber origin, content and mechanical characteristics, water vapour absorption and biodegradability was established. Optimal characteristics of elaborated eco-composites were obtained by use of flax combing with fiber content ~ 30 wt. %.
Evaluation of Silver Ion Bioavailability from Silver Doped Hydroxyapatite
Authors: Dubnika Arita , Rudovica Vita
Published: March 2014

Thein vitrobehavior of silver doped hydroxyapatite (HAp/Ag) prepared by two wet precipitation routes were studied in water and simulated body fluid (SBF). In order to evaluate the silver ion bioavailability from HAp/Ag, the samples were soaked in SBF or water and kept at 37°C for fixed periods of time up to one year. After fixed periods of time, analyses of SBF and water solutions were performed and silver ion concentration within the solutions determined. According to silver release data from dense and porous HAp/Ag ceramic scaffolds, release rate of silver ions were reduced in water as the ion exchange there was slower compared to SBF solution. X-ray diffraction and scanning electron microscopy analysis approved the formation of hydroxyapatite type layer on the surfaces of scaffolds after one year soaking in SBF.
Fast Setting Pre-Mixed Calcium Phosphate Bone Cements Based on α-Tricalcium Phosphate
Authors: Irbe Zilgma , Krieke Guna , Salma-Ancane Kristine , Berzina-Cimdina Liga
Published: March 2014

Conventional calcium phosphate bone cements are self setting water based pastes. Recently pre-mixed calcium phosphate bone cements have been proposed that have non-aqueous fluid as liquid phase of the paste. Such cements thus only start setting reaction in contact with body fluids. In this work the properties (cohesion, compressive strength, phase composition) of pre-mixed calcium phosphate cements based on α-tricalcium phosphate and calcium dihydrogen phosphate monohydrate are described. Properties of several cement compositions are examined and compared to properties of β-tricalcium phosphate and calcium dihydrogen phosphate monohydrate based cements. It was found that α-tricalcium phosphate and calcium dihydrogen phosphate monohydrate based cements have higher compressive strength (10 - 15 MPa) than corresponding β-tricalcium phosphate and calcium dihydrogen phosphate monohydrate based cements (10 - 6 MPa). Out of examined cement paste liquids (glycerol, polyethylene glycol and polypropylene glycol) cements using glycerol as the liquid phase had higher compressive strength and are more cohesive.
Nanostructured Calcium Phosphates for Biomedical Applications
Authors: Vecbiskena Linda , de Nardo Luigi , Chiesa Roberto
Published: March 2014

This work is focused on the phase transformation from amorphous calcium phosphate (ACP) to nanostructured hydroxyapatite (HA) or tricalcium phosphate (TCP). Amorphous calcium phosphates with Ca/P molar ratio near 1.67 and 1.5 were synthesized by wet-chemical precipitation method and treated with ethanol. Upon thermal treatment, ACP clusters about 50 nm create a nanostructured HA or TCP. The highlights of this research: The precipitate treatment with ethanol provided a pure α-TCP that was found to be stable up to 1000 °C. HA is obtained from the ACP precursor synthesized using also ammonium dihydrogen phosphate.
Alkaline Activated Material for pH Control in Biotechnologies
Authors: Ruģele Kristīne , Bumanis Girts , Bajare Diana , Lakevičs Vitalijs , Rubulis Jānis
Published: March 2014

By using industrial aluminium recycling waste, recycled silicate glass from outworn fluorescence lamp recycling plant, calcined kaolinite clay supplemented with alkali activator with different silicate modulus the new type of porous material for biotechnologic processes without the need for additional equipment for pH control was researched. This controlled-release system contains an alkali activated matrix in which NaOH crystals are encased. In this study ability to release NaOH per time in water according to material composition and structure were investigated. Three alkaline activated materials AAM 7.5, 10 and 12.5, with different alkali activator content were characterized.
Composite Material for Effective Cheese Whey Anaerobic Digestion
Authors: Ruģele Kristīne , Bumanis Girts , Eriņa Laura , Erdmane Daira
Published: March 2014

The effect of a composite material additive on the methane production from sweet whey was investigated. Two fractions 2-4 mm and 4-5.6 mm and two modifications by age of material were researched. Whey concentrations of 10 and 15% were used with 0.6 g composite material addition per g of volatile solids. The additions of composite materials resulted in significant biomethane potential increasing.
Effect of Shaping Method and Heat Treatment on Microstructure and Thermoelectric Properties of Titanium Dioxide
Authors: Rubenis Kristaps , Pura Agnese , Teteris Valdis , Locs Janis , Ozolins Jurijs
Published: March 2014

The TiO2samples were obtained by two different shaping methods: cold isostatic pressing and cold extrusion, sintered in air at 1373 K, 1573 K, 1773 K and annealed under vacuum at 1373 K. Differences in density, microstructure and thermoelectric properties were observed between the samples depending on the shaping method used. With increase in sintering temperature the electrical conductivity of all samples increased while the Seebeck coefficient decreased. Great microstructural differences were observed between the surface and bulk of the samples made by each of the shaping techniques. It was found that microstructural differences between surface and bulk of the samples affect their thermoelectric properties.
Effect of the Acid Hydrolysis Temperature on the Conversion of Birch Wood Hemicelluloses into Furfural
Authors: Brazdausks Prans , Vedernikovs Nikolajs , Puke Maris , Kruma Irena
Published: March 2014

In this study, a new dilute sulphuric acid hydrolysis method was used for hemicelluloses secession from birch wood. The furfural extraction was investigated at different process temperatures (132°C ‑ 162°C, increasing it by 5°C) and at constant amount of catalyst 3.0%, calculated on oven‑dried wood. The greatest amount of furfural 11.09%, which is 75.6% from the theoretical possible yield, was formed at temperature 147°C after 90 min from the beginning of the birch wood pentoses monosaccharides dehydration process.
Development and Research of Thermal Insulation Materials from Natural Fibres
Authors: Vaitkus Saulius , Karpavičiūtė Rūta , Vėjelis Sigitas , Lekūnaitė Lina
Published: March 2014

Natural fibres from flax and hemp are used as raw materials for efficient thermal insulation. In current work, tests were carried out using chopped and combed long flax fibres as well as chopped and combed long hemp fibres. Investigations have shown that thermal conductivity of natural fibres depends on their preparation method (combing, chopping) and materials density.
High Temperature Cyclic Impact/Abrasion Testing of Boiler Steels
Authors: Priss Jelena , Klevtsov Ivan , Dedov Andrei , Antonov Maksim , Rojacz Harald , Badisch Ewald
Published: March 2014

In the present study the high temperature impact/abrasion resistance of several boiler steels which are used in Estonian power plants were determined experimentally using the High Temperature Cyclic Impact Abrasion Test (HT-CIAT) at 500 and 600°C. Results indicate a strong dependence of the wear resistance on the materials microstructure and formation of the mechanically mixed layer with incorporated abrasive particles.
Abrasive Wear Resistance of HVOF Sprayed and PTA-Welded Hardmetal Hard Phase Reinforced Metal-Matrix Based Coatings
Authors: Tarbe Riho , Kulu Priit , Žikin Arkadi , Surženkov Andrei
Published: March 2014

The aim of the current study was to elaborate and compare abrasive wear resistance of thick metal matrix based deposited coatings. To produce metal matrix composite (MMC) coatings, experimental powders made by mixing commercial nickel and iron based powders with recycled hardmetal powder were used. The usage of recycled hardmetal as an initial material can significantly decrease the cost of production, improve the mechanical characteristics of coatings and consequently increase their wear resistance. Based on structural studies the optimal content of 40 vol% hard phase was selected. Plasma transferred arc (PTA) hardfacing and high velocity oxyfuel (HVOF) spraying were used as deposition technologies. The behavior of coatings by abrasive rubber wheel wear (ARWW ) (based on G 65 standard), abrasive impact wear (AIW) and abrasive erosion wear (AEW) (based on GOST standard) was investigated. The results showed that the wear resistance of experimental PTA hardfacings at high angle impact wear conditions is notably higher than of HVOF sprayed coatings.
Characterization of Impact Abrasive Wear Produced by Different Rocks
Authors: Petrica Marcela , Peinsitt Thomas , Badisch Ewald
Published: March 2014

In industry, core components such as crushers, miner feeder devices and impact stone breakers are exposed to heavy wear which involves mechanisms such abrasive wear and / or impact abrasion. The purpose of this work is to identify complex wear mechanisms that occur in such conditions and to correlate them with the properties of typical abrasives found in mining environments.
Deformation-Burst Schemes of 3-Piece Aerosol Containers
Authors: Ratas Kaarin , Peetsalu Priidu
Published: March 2014

This paper focuses on a three-piece steel aerosol container deformation and burst pressure comparison and tries to point out some topics which could help to improve pressure resistance of an aerosol container. Different material thicknesses are tested to find out which one could improve the overall aerosol container performance the most. This research shows that thinner material can give satisfying pressure resistance results what is important when trying to reduce material costs but further research will be needed to get necessary knowledge of deformation-burst schemes in depth.
Influence of Material Internal Stresses to the Coefficient of Friction
Authors: Rags Didzis , Kamols Andris , Linins Oskars , Boiko Irina
Published: March 2014

The aim of this paper is to calculate and compare both tangential and normal internal stresses in contacting area of two spherical bodies in contact. The results of these calculations have a practical use in further research of coefficient of friction in relation to the surface roughness asperities of contacting bodies.
Bi2WO6 Nanoparticles Prepared by Combustion Synthesis with Different Fuels and their Photocatalytic Activity
Authors: Kodols Maris , Didrihsone Sabine , Grabis Janis
Published: March 2014

The influence of glycine, glycerine, ethylene glycol and citric acid fuel and their ratio to NO3- on formation and dispersity of Bi2WO6 nanoparticles prepared by combustion synthesis has been studied. The pure crystalline Bi2WO6 with specific surface area 24,8 m2/g and crystallite size of 28 nm was obtained by using glycerine as fuel at its ratio to NO3- of 0,67. The photocatalytic activity of the prepared Bi2WO6 in degradation of methylene blue depended on its specific surface area of samples and solution pH.
The ethics of absolute relativity: An eschatological ontological model for interpreting the Sermon on the Mount
Authors: Van Oudtshoorn Andre
Published: March 2014

Jesus� imperatives in the Sermon on the Mount continue to play a significant role in Christian ethical discussions. The tension between the radical demands of Jesus and the impossibility of living this out within the everyday world has been noted by many scholars. In this article, an eschatological-ontological model, based on the social construction of reality, is developed to show that this dialectic is not necessarily an embarrassment to the church but, instead, belongs to the essence of the church as the recipient of the Spirit of Christ and as called by him to exist now in terms of the coming new age that has already been realised in Christ. The absolute demands of Jesus� imperatives, it is argued, must relativise all other interpretations of reality whilst the world, in turn, relativises Jesus� own definition of what �is� and therefore also the injunctions to his disciples on how to live within this world. This process of radical relativisation provides a critical framework for Christian living. The church must expect, and do, the impossible within this world through her faith in Christ who recreates and redefines reality. The church�s ethical task, it is further argued, is to participate with the Spirit in the construction of signs of this new reality in Christ in this world through her actions marked by faith, hope and love.
Spectral analysis and long-time behaviour of a Fokker-Planck equation with a non-local perturbation
Authors: Stürzer Dominik , Arnold Anton
Published: March 2014

In this article we consider a Fokker-Planck equation on

\mathbb R^d

with a non-local, mass preserving perturbation. We first give a spectral analysis of the unperturbed Fokker-Planck operator in an exponentially weighted

L^2

-space. In this space the perturbed Fokker-Planck operator is an isospectral deformation of the Fokker-Planck operator, i.e. the spectrum of the Fokker-Planck operator is not changed by the perturbation. In particular, there still exists a unique (normalized) stationary solution of the perturbed evolution equation. Moreover, the perturbed Fokker-Planck operator generates a strongly continuous semigroup of bounded operators. Any solution of the perturbed equation converges towards the stationary state with exponential rate

-1

, the same rate as for the unperturbed Fokker-Planck equation. Moreover, for any

k\in\mathbb N

there exists an invariant subspace with codimension

k

(if

d=1

) in which the exponential decay rate of the semigroup equals

-k

.
De auteur en beeldende kunstenaar Armando in de jaren 1954-1960: de beginjaren van een multitalent
Authors: Favié Trudie
Published: March 2014

In this paper, an attempt is made to sketch the first years of the artistic career of the Dutch writer and painter Armando (1929) in relation to the scrapbooks he made himself from 1954 to 1973. In addition to an introduction to the themes and works of this multi-talented artist, the paper confirms that the scrapbooks, especially the first that was made in 1954-1960, illustrate the image of an aggressive and provocative Armando. Frustration about negative criticism of his poems has lead to aggression and bolstering this attitude in the composition of the scrapbook.
Nederlands later geleerd: gebruik van lidwoorden en flexie van bijvoeglijke naamwoorden door Duitstalige kinderen en volwassenen
Authors: Ziemann Hendrikje , Weerman Fred , Ruigendijk Esther
Published: March 2014

Both German children and adults acquiring Dutch as a second language are tested on their production of determiners and adjectival inflection in attributive position. Both groups tend to overgeneralise the common determiner (de). Children overgeneralise the inflected adjective, while adults make mistakes in two directions: they overgeneralise both the inflected and the uninflected adjective. This age effect is reminiscent of what is found for L2 learners of Dutch with a Turkish and a Moroccan Arabic background (see Blom, Polišenská & Weerman 2006, 2008b), but there are differences as well. The most conspicuous difference is that the German children seem on the right track with respect to the uninflected adjective, whereas the Turkish and Moroccan Arabic children fossilise the inflected variant. It is argued that the L1 background cannot explain this difference and in general only plays a marginal role in the acquisition of Dutch determiners and adjectival inflection. Instead it is suggested that the quality and the quantity of the Dutch input plays a role, alongside the age difference.