Preparation technology of ultra-fine powders of Auricularia auricular

Conventional mechanical method and mechanical method combined with vacuum freeze-drying technology were used to make the ultra-fine powders of edible fungus (Auricularia auricular). The content of basic nutrients, amino acid, micro structure and their properties of raw edible fungus and the edible fungus powders obtained with the two methods were analyzed and compared. The granularity size and micro-structure of the pulverized samples were analyzed by SEM and TEM technology. The average granularity size of the edible fungus powder obtained with mechanical method was 1–5 μm, while that obtained with mechanical method combined with vacuum freeze-drying process was 0.5–1 μm. The ultra-fine powders of edible fungus obtained with the two methods had better water recovery capability and quality, and their preserving time was longer than that of raw edible fungus. All the properties of the ultra-fine powders of edible fungus obtained with the vacuum freeze-drying technology were evidently superior to that of the conventional mechanical method. Keywords Auricularia auricula - Edible fungus - Ultra-fine powders - Vacuum freeze-drying CLC number TS205 Document code B Biography: YANG Chun-yu (1975), female, Ph. D. in Engineering Technology Center of Forestry and Wood Workine, Machinery, Northeast Forestry University, Harbin 150040, P. R. China.Responsible editor: Zhu Hong

Optimal Conditions for Preparing Ultra-Fine CeO_2 Powders in A Submerged Circulative Impinging Stream Reactor

Cerium carbonate powders were produced in a submerged circulation impinging stream reactor （SCISR） from Ce（NO3）3· 6H2O. NH4HCO3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide （CeO2） powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce（NO3）3 and NH4HCO3 solutions were 02,5 and 0.3 mol · L^-1, respectively. The concentration of PEG4000 added in these two solutions was 4 g · L^-1. The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r · min^- 1,80 ℃, 20 min, 5 - 6, 5 min and 1 h, respectively. The final product, CeO2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500 ℃. The finally produced CeO2 powders were torispherical particles with a narrow size distribution of 0.8 -2.5 μm. The crystal structure of CeO2 powders belonged to cubic crystal system and its space point 5 group was OH^5-FM3M. Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor （STR）.

DYNAMIC RHEOLOGICAL BEHAVIOR OF POLYPROPYLENE FILLED WITH ULTRA-FINE POWDERED RUBBER PARTICLES

Dynamic rheological characteristics of polypropylene (PP) filled with ultra-fine full-vulcanized powdered rubber (UFPR) composed of styrene-butadiene copolymer were studied through dynamic rheological measurements on an Advanced Rheometric Expansion System (ARES). A specific viscoelastic phenomenon, i.e. 'the second plateau', appeared at low frequencies, and exhibits a certain dependence on the amount of rubber particles and the dispersion state in the matrix. This phenomenon is attributed to the formation of aggregation structure of rubber particles. The analyses of Cole-Cole diagrams of the dynamic viscoelastic functions suggest that the heterogeneity of the composites is enhanced on increasing both particle content and temperature.

An improved sodium silicate binder modified by ultra-fine powder materials

This paper presents a new method of modifying sodium silicate binder with ultra-fine powders. The sodium silicate binder modified by ultra-fine powder A and the organic B can reduce the addition amount of the binder. The results indicate that the 24 h strength has increased by 39.9% at room temperature and the residual strength has decreased by 30.7% at 800℃, compared to the conventional sodium silicate. An available material to improve the moisture resistance was also found by adding about 2% more inorganic C, and it can increase the moist strength by 20%. In the end, the microanalyses are given to explain the modifying machanism, i. e., the ultra-fine powder A can refine the sodium silicate binder to avoid holes in the binder bond, which can increase the 24 h strength at room temperture, and can lead to more cracks in the bond after the molding sand is heated to 800℃. This is because of the stress caused by the new eutectic complex of modified sodium silicate binder.

Hydrogen Reduction:A Novel Method of Synthesizing Ultra-fine Chromic Oxide Powder

The ultra-fine chromic oxide powder was prepared by a novel gas-solid reduction reaction.Na2CrO4 was firstly reduced with hydrogen at 400-600 ℃.The obtained reduction products,mainly the mixture of NaCrO2 and sodium hydroxide（NaOH）,were converted into chromic oxide through hydrolysis followed by calcination.The obtained chromic oxide product was characterized by powder X-ray diffraction（XRD） and SEM.The results show that the hydrolysis process of sodium chromite is the key step and lower reduction temperature helps intensify the hydrolysis process.

Strengthening of HT250 by modified ultra-fine ceramic powders

In this study, three kinds of modified ultra-fine ceramic powders marked A, B and C, which were prepared by each of three different modifiers mixing with a commercial SiC, were added to HT250 cast iron, respectively, and the effects of the modified ultra-fine ceramic powders on microstructure, mechanical properties and wear resistance were studied. Metallographic examination, tensile test, scanning electron microscopy, and three-dimensional surface topography were applied to analyze and compare the samples containing modified powder with the original samples. The results showed that the most obvious modification effect among the powders was seen in the sample containing powder A, with the graphite and eutectic cells being refined, the tensile strength being increased by 36.9%, and the wear resistance being improved by 45.5% and 47.2% under loads of 150 N and 300 N, respectively. The improvements of mechanical properties and wear resistance in the HT250 cast iron with the modified ultra-fine ceramic powders were attributed to the synergistic effect of the grain refinement with the powder acting as a hard particle phase and the lubrication by the graphite.

Effects of tourmaline on microstructures and photocatalytic activity of TiO_2/SiO_2 composite powders

The SiO2/TiO2 composite powders including mineral tourmaline powders (T/SiO2/TiO2) were prepared from a sol made by a two-step hydrolysis method, using metasilicate ester as precursor. The powders were characterized by scanning electron microscopy (SEM). The photocatalytic activity of the sample was evaluated by the photocatalytic degradation of methyl orange. The effects of heat-treatment on the photocatalytic activity were discussed. It is found that the T/SiO2/TiO2 composite powders show higher photocatalytic activity when including 10% SiO2 and 4% tourmaline. Moreover, the photocatalytic mechanism of tourmaline on the powders was proposed.

Preparation of Ultra-fine Salbutamol Sulfate Particles by Reactive Precipitation and Characterization of Dry Powder Inhalant

The preparation of ultra-fine particles of salbutamol sulphate （SS） was accomplished with a reactive precipitation pathway, in which salbutamol and sulphuric acid were Used as reactants with the solvents of ethanol.The effects of sulphuric acid concentration, reaction temperature, stirring rate, and reaction time onthesize of the particle were investigated. A binary mixture composed of lactose and SS was prepared to evaluate SS. The results showed that ultra-fine SS particles with controlled diameters ranging between 3 μm and 0.8 μm and with a narrow distribution could be achieved. The morphology consisting of clubbed particles wassuccess.fully obtained. The purity of the particles reached above 98% with-UV detection. The dose- of dry powder inhalation was obtained by blending the particles with recrystallized lactose, which acted as a carrier. The deposition quantity of the drug in breathing tract was estimated using a twin imPinger apparatus. Compared with the Shapuer powder （purchased in the market）, the results showed that SS_particles had more quantifies.subsided in simulative lung.. _

Polar Mineral Tourmaline and Its Effect on the Photocatalysis of Nano-TiO2

The mechanism for tourmaline powder improving the photocatalysis effect of nano-TiO2 was studied by electron-spin resonance (ESR). It is found that the intensity of the signal of hydroxyl free radical produced by the mixture of the tourmaline and nano-TiO2 through 355nm wavelength ultraviolet radiating is increased. Under natural light, the mixture of nano TiO2 and tourmaline powder in a certain weight ratio can improve the effect of decomposing methyl orange that proved that the ESR result was right. The tourmaline particle could promote the photocatalysis of nano-TiO2. This result may be due to the surface electric field of the tourmaline, which can absorb the particle of nano-TiO2 and make the electron inspired by photon transfer from the inner of nano-TiO2 particle to its surface, and even make the electron transfer into tourmaline particle.

Preparation of Well Dispersed and Ultra-Fine Ce(Zr)O_2 Mixed Oxide by Mechanochemical Processing

Ultra-fine CeO_2-ZrO_2 mixed oxide was successfully synthesized by wet-solid phase mechanochemical processing, Ce_2(CO_3)_3·8H_2O, ZrOCl_2·xH_2O and ammonia were used as reactants. It is found that the crystalline Ce_2(CO_3)_3·8H_2O and ZrOCl_2·xH_2O are changed to amorphous cerium and zirconium hydroxide precursor after milling with ammonia, and Ce_(0.15)Zr_(0.85)O_2 mixed oxide with pure tetragonal phase structure and medium particle size(D_(50))less than 1μm is formed by calcining precursor over 673 K. The XRD patterns indicate that the crystal unite size increases with rising calcining temperature due to crystal growth. However, the particle size and BET surface area of the Ce(Zr)O_2 mixed oxide decreases with rising calcining temperature, which may be attributed to the contract of particles and the vanish of holes inside grains.

Synthesis and Characterization of Nano-sized Boron Powder Prepared by Plasma Torch

Hydrogen thermal plasma jet was employed to prepare nano-sized boron powder with hydrogen reduction of BCI3. The maximum yield of nano-sized boron powders was about 50% with the operational conditions of H2/BCl3 of 4.5：1, total feed of 4.9 m3/h, and plasma power of 25 kW. The samples were analyzed by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM）, and inductively coupled plasma - mass spectrometry （ICP-MS）, inductively coupled plasma - atomic emission spectrometry （ICP-AES）, inductive combustion infrared absorption （ICIA） and infrared thermal conductivity of oxygen and nitrogen analyzer （ITCA）. The results show that the boron powders have different crystal structures with higher dispersion and purity. The average diameter is about 50 nm, and the purity is 90.29% or so. This new technology can use simple process to produce high quality boron powders, and is feasible for industrial production.

Preparation of Reactive Powder Concrete Using Fly Ash and Steel Slag Powder

To decrease the cement and SF content of RPC by using ultra-fine fly ash （UFFA） and steel slag powder （SS）, the effect of these mineral admixtures on compressive strength of RPC were investigated. The experimental results indicate that the utilization of UFFA and SS in RPC is feasible and has prominent mechanical performance. The microstructure analysis （SEM and TG-DTG-DSC） demonstrated that the excellent mechanical properties of RPC containing SS and UFFA were mainly attributed to the sequential hydration filling effect of the compound system.

Preparation of Ultrafine Tungsten Powder by Sol-Gel Method

Sol-gel method was employed for the preparation of nanoscale tungsten powder. The effects of different preparation conditions on particle size were discussed and the optimum preparation condition was found. The products were characterized by X-ray diffraction, scan electron microscopy and so on. The results show that the intermediate is monoclinic WO3, its particle shape is approximately spherical, and the particle size distribution is narrow. The average particle size is about 60 nm. After deoxidization, WO3 turns into cubic tungsten powder with small particle size （average particle size about 120 nm） and narrow size distribution.

Crystal Structure of Ba_xSr_1-xTiO₃Fine Powder

Various compositions of the system BaxSr1-xTiO3 (BST) have been elaborated both as fine powders and ceramic monoliths, using the co-precipitation route within a warmed supersaturated solution of oxalic acid. The appropriate stoichiometry was determined from the mixtures of precisely titrated aqueous solutions of cations chlorides (SrCl2, BaCl2, and TiCl4). The reason of this process was to apply low sintering temperature in production of BST samples with ultra-fine powders. These powders primarily calcined at (850°C) for (5 hr) were used to elaborate ceramics after pellets sintering at (1200°C) during (8 hrs). Indeed, XRD patterns were confirmed that the samples are a pure phase and a perovskite cubic structural type at (x = 0, 0.5, 0.6). Whereas, (x = 0.7, 0.8, 0.9, 1) showed a tetragonal phase. There is agreement between the FTIR and XRD analysis, by the relation of the wave vector (K) and lattice constant. It was deduced a stimulated relation between (x) and (K). The results of TEM, they were clear that the lowest particle sizes investigated of BST powders nearly (36 - 50 nm).

Preparation and properties of Nd:YAG ultra-fine powders

Ultra-fine Nd：YAG powders with different doping concentrations were synthesized by sol-gel combustion method. The pure Nd：YAG could be prepared at the low temperature of 900℃. Ethanol could improve the dispersity of powders, and the average size of the ultra-fine powders was around 250 nm. The reflection spectrum showed that there were several apparent characteristic absorption peaks and the intensity of these peaks enhanced with the increasing concentration of Nd^3＋. The luminescence spectrum, which was excited by 808 nm wavelength, exhibited several obvious emission bands in the range of 900-1150 nm. The emission intensity of Nd：YAG powders increased until the Nd content was above 3 mol.% due to the fluorescent quenching effect.

A new method of preparing NdB_(6)ultra-fine powders

Combustion synthesis method was used to prepare NdB_(6)ultra-fine powders with B_(2)O_(3),Nd_(2)O_(3)and Mg powders as the raw materials.The basic thermody-namic data of NdB_(6) were estimated.The standard forma-tion heat of NdB_(6) is-357.48 kJ·mol^(-1).The values of the heat capacity and the standard entropy are 96.87 and 86.60 J·K^(-1)·mol^(-1),respectively.The adiabatic tempera-ture of the reaction is 2726 K,which is higher than the thermodynamic criterion of 1800 K.This indicates that the combustion synthesis reaction of the B_(2)O_(3)-Nd_(2)O_(3)-Mg system could spontaneously take place by itself to generate NdB_(6).The NdB_(6) powders were characterized by X-ray diffractometer(XRD),scanning electron microscopy(SEM)and differential scanning calorimetry-thermo-gravimetry(DSC-TG).The results indicate that the com-bustion products consist of NdB_(6),MgO,and a few Mg_(3)B_(2)O_(6)and Nd_(2)B_(2)O_(6).The leached products consist of single NdB_(6) phase,and its purity is 98.6 wt%.When the sample preparation pressure is 20 MPa,the average parti-cle size of NdB_(6) powders is less than 500 nm.The antioxidant ability of NdB_(6) is very strong,which is oxi-dized step by step.The apparent activation energies of the oxidation reactions are 986.14 and 313.83 kJ·mol^(-1),respectively.In addition,the reaction orders are 4.10 and 3.75,respectively.

热处理对电气石矿物粉体表面自由能的影响

将电气石粉体在500～800℃焙烧处理,用表面张力仪测量热处理前后粉体对水、乙醇、30%乙二醇水溶液的接触角,并用Wu氏方程计算电气石粉体的表面自由能及组成。用X射线衍射仪、X光电子能谱仪等研究热处理影响电气石粉体表面自由能的机理。结果表明:随着热处理温度升高,电气石粉体的表面自由能及极性分量逐渐增加,且在800℃具有最大值;产生这种现象的原因在于随着热处理温度升高,电气石粉体表面铁元素逐渐从二价向三价转化,其晶胞体积逐渐缩小、电极性增加。

电气石远红外辐射对水表面张力的影响

用固液分置法排除电气石自发电场对水的影响,研究了极性晶体电气石辐射的远红外线对水表面张力的影响规律。结果表明:电气石辐射的远红外线作用于水分子产生共振,可削弱水分子间氢键作用,从而使水表面张力降低。室温时,当电气石粉体的中位粒径(D50)为4.0～6.5μm时,随着电气石辐射远红外线对水作用时间延长,水的表面张力逐渐降低。D50为4.0μm,电气石粉体与水的质量比[m(t)/m(w)]不低于0.5时,随着辐射时间的延长水表面张力明显降低。D50为6.5μm,m(t)/m(w)为0.5时,水表面张力由初始值72.571mN/m降为72.049mN/m。

电气石粉体电磁屏蔽性能研究

电气石是一种具有自发极化性质的矿物材料,具有独特的电磁学性能。通过对比实验,将电气石粉体制成了复合涂料,测试证实了电气石粉体的电磁屏蔽性能。

负离子粉体材料的超细化和表面改性研究

采用聚羧酸盐为表面改性剂,用玛瑙球为研磨介质,研究电气石矿物粉末的研磨改性工艺,优化了最佳的研磨工艺条件,并对湿法研磨改性的电气石粉末进行了粒度分析测试。红外光谱显示,研磨改性后的电气石粉末表面带有聚羧酸基团,可进一步增进电气石粉末与各种材料的相容性能。改性后电气石粉末的负离子释放量达600个/cm3。