Synthesis of Neodymium-Doped Yttrium Aluminum Garnet (Nd∶YAG) Nano-Sized Powders by Low Temperature Combustion

The homogeneously dispersed, less agglomerated (Nd0.01Y0.99)3Al5O12 nano-sized powders were synthesized by the low temperature combustion (LCS), using Nd2O3, Y2O3, Al(NO3)3·9H2O, ammonia water and citric acid as starting materials. This method effectively solves the problems caused by solid-state reaction at high temperature and hard agglomerates brought by the chemical precipitation method. The powders were characterized by TG-DTA, XRD, FT-IR, TEM respectively and the photoluminescence (PL) spectra of (Nd0.01Y0.99)3Al5O12 green and sintered ceramic disks were measured. The results show that the forming temperature of YAG crystal phase is 850 ℃ and YAP crystal phase appearing during the calcinations transforms to pure YAG at 1050 ℃. The particle size of the powders synthesized by the LCS is in a range of 20～50 nm depending on the thermal treatment temperatures. The effectively induced cross section (σin) with the value 4.03×10-19 cm2 of (Nd0.01Y0.99)3Al5O12 ceramics is about 44% higher than that of single crystal.

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.

The Effect of Hydroxyapatite Ultrofine Powder on the Immunity Function of Tumor-bearing Mice

The inhibitory effect of hydroxyapatite ultrofine powder on tumor and the effect on the immunity function of body were investigated. The levels of IL 2 in the spleen cells and serum TNF levels in the tumor bearing mice at the 7th day and 14th after peritoneal injection of HAUFP were detected by using the methods of colorimetric analysis of MTT and crystal purple decoration, respectively. The disappearance of the ascites of the mice was observed. The results showed that the levels of IL 2 and TNF in the tumor bearing mice were higher obviously in the drug treated group than in the control group , the ascites growth was inhibited. It was suggested that HAUFP could increase the levels of IL 2 and TNF of the tumor bearing mice and improve the immune function of body.

DNADam ageEffectsofHydroxyapatiteUltrofinePowderonW-256 Sarcom a Cells and Lym phocytes in Rats

To explore the anticancer mechanism and DNA damages of hydroxyapatite ultrofine powder (HAUFP) on lymphocytes of rats, DNA damages in W 256 sarcoma cells and lymphocytes of rats were measured by single cell gel electrophoresis (SCGE). The results showed that HAUFP damaged DNA of W 256 sarcoma cells obviously but only cause slight damage of DNA of lymphocytes in rats. It is suggested that HAUFP selectively damaged DNA of tumor cells with only mild damage of lymphocyte DNA. HAUFP has powerful anticancer effect and little genetic toxicity.

Micro-aluminum powder with bi-or tri-component alloy coating as a promising catalyst:Boosting pyrolysis and combustion of ammonium perchlorate

A novel design of micro-aluminum(μAl)powder coated with bi-/tri-component alloy layer,such as:Ni-P and Ni-P-Cu(namely,Al@Ni-P,Al@Ni-P-Cu,respectively),as combustion catalysts,were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate(AP)at a lower temperature in aluminized propellants.The microstructure of Al@Ni-P-Cu demonstrates that a three-layer Ni-P-Cu shell,with the thickness of~100 nm,is uniformly supported byμAl carrier(fuel unit),which has an amorphous surface with a thickness of~2.3 nm(catalytic unit).The peak temperature of AP with the addition of Al@Ni-P-Cu(3.5%)could significantly drop to 316.2℃ at high-temperature thermal decomposition,reduced by 124.3℃,in comparison to that of pure AP with 440.5℃.It illustrated that the introduction of Al@Ni-P-Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol.The laser ignition results showed that the ignition delay time of Al@Ni-P-Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni-P/AP(118 ms),decreased by 33.90%.Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions(7597.7 J/g)of Al@Ni-P-Cu,resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion.Moreover,it is believed to provide an alternative Al-based combustion catalyst for propellant designer,to promote the development the propellants toward a higher energy.

The Preparation and Synthetic Mechanism of Hydroxyapatite Powder by Simple Sol-Gel Method

Hydroxyapatite powder was prepared by sol-gel method using the calcium nitrate tetrahydrate and pentoxide us reactant. The effects of main processing parameters such us reagent, concentration, temperature etc on the synthesis of hydroxyapatite were investigated. The synthetic mechanism was also studied. The results showed that main optimized parameters were us follows ： 2 M ethanol solution of P2 05 and 4 M ethanol solution Ca（ NO3 ）2 ·4H2O, 12- 24 h of aging time, 500℃ sintered temperature. X-ray diffraction and Fourier transform infrared spectra results showed that the mixtures were composed of amorphous hydroxyapatite, Ca （ NO3）2, PO（ OH）3-x（ OR）x, bellow 400℃. The pure hydroxyapatite powder were prepared at 500℃ for 30 nun. The aging of the sol influenced the purity greatly. The CaO phase was observed from the powder without aging. This process with cheap reactants was simple and the advantages offered by this process made it possible to produce the uniform fine powder in large quantity.

Preparation and Sinterability of Mn-Zn Ferrite Powders by Sol-Gel Method

Mn-Zn spinel ferrites were synthesized by sol-gel method. Effects of calcined temperature on structure and particle size of MnZnFe2O4 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns indicate that the ultra fine Mn-Zn ferrite exhibits a spinel crystal structure. SEM images show that the powder fired at 900 ℃ for 2 h has an average diameter of 60～90 nm. The particle size becomes larger with the increasing of calcined temperature and the distribution of particle becomes even more homogeneous. Sintering behaviors of synthesized ferrite powders depend on the powder characteristics and high temperatures have induced the good crystallization of particles.

Exploratory Trial to Evaluate the Hydroxyapatite Layer Formed by a New Dental Treatment System

Objective: A powder jet deposition (PJD) process can be used to create a thick hydroxyapatite (HA) layer on the human tooth surface. The purpose of this exploratory trial was to evaluate the safety and efficacy of the hydroxyapatite layer formed by a new dental treatment system for cases of caries, dentin hypersensitivity, or discolored teeth. Methods: A single facility, non-blinded study comparing before and after treatment interventions, without a comparative control, was conducted. A rubber dam was attached to the teeth followed by the application of Vaseline to the gingival margins. Extra- and intra-oral vacuums and a saliva discharge tube were used to spray HA powder over the target site with the PJD equipment. Results: The formation of an HA layer tended to reduce pain on exposure to cold water and air in the cases with caries, and increase brightness and satisfaction in the cases with tooth discoloration. The pain on exposure to air was significantly reduced in the cases with dentin hypersensitivity. PJD was not observed to cause any inflammation of the surrounding gingiva or pulpal symptoms. Conclusions: HA is anticipated to reduce the need for repeat treatment by offering superior compatibility with the tooth substance when compared with other dental materials.

Characterization of terbium-doped nano-hydroxyapatite and surface modification

The control synthesis of nanoparticles was the implementation process of material ideal design. Nano-hydroxyapatite(HAP) was prepared by a hydrothermal method with calcium nitrate and diammonium hydrogen phosphate as raw material, to study its characteristics for morphology modification by arginine-functionalization and doping with rare earth such as Tb^(3+). The crystallization, grain size and dispersibility of the sample HAP were analyzed and discussed. The results show that the surface Zeta potential of arginine-functionalized HAP is changed, and the growth rate of HAP is inhibited to a certain extent during the synthesis. The structure of HAP/Arg is not affected during the synthesis by a small amount of rare earth ions doped such as Tb^(3+), and has a single phase of HAP with good dispersibility. The synthesized HAP is also of nano-sized level. Nano-hydroxyapatite argininefunctionalized and doped with rare earth such as Tb^(3+), is suitable for the application of gene delivery as a gene carrier.

Microstructure and phase composition of Ti-based biocomposites with different contents of nano-hydroxyapatite

Nano-hydroxyapatite(nHA) and titanium(Ti) powders with different ratios were prepared by mechanical ball milling,and then sintered in vacuum environment. The microstructure and phase composition of Ti-based biocomposites with different contents of nHA(5% and 10%,in volume fraction) were investigated. Meanwhile,the phase composition of pure Ti was studied for contrast. The results show that Ti phase forms a finer continuous network microstructure with few porous after milling and sintering. The higher amount of nHA powders are added,the higher amount of porous are achieved,while the fracture morphology becomes coarser. The specimen with contents of 10% nHA has serious interface reaction after sintering at 1 100 ℃,it varies with the pure Ti specimen. Combined with the XRD and EDS analysis,it can be founded that elements Ca,P,O and Ti diffuse on the interface,and the phases of Ti,Ti2O,Ti5P3,CaTiO3 and TiOx can be ascertained in nHA/Ti composites.

Preparation and Characterization on Nano- Sized Barium Titanate Powder Doped with Lanthanum by Sol-Gel Process

The nano-sized BaTiO3:La3+ powders were prepared by sol-gel process using butyl phthalate, barium acetate and lanthanum oxide as raw material, and these samples were tested by means of TG-DTA, XRD and SEM. The results indicate that with the annealing temperature and the doped concentration rising, the powders' particle sizes will increase and decrease respectively. When annealing temperature is 900 ℃ and doped concentration is 7%, the phase is cubic without other phases, and the particle size of power is 43.34 nm.

Corrosion properties in a simulated body fluid of Mg/β-TCP composites prepared by powder metallurgy

Magnesium matrix composites （MMC） reinforced with 5wt% tricalcium phosphate （TCP） particles were prepared by powder metallurgy. Pure magnesium （CP-Mg） was fabricated by the same procedure for comparison. Scanning electron microscopy and en- ergy-dispersive X-ray spectroscopy analyses revealed that TCP particles were distributed homogeneously in the MMC. In order to investi- gate the corrosion properties, MMC samples were immersed in a simulated body fluid （SBF） at 310~0.5 K for 72 h. The mass loss of the samples in SBF and the pH values of the SBF were evaluated. Moreover, electrochemical measurements were conducted in the SBF. It was shown that the corrosion rate of the MMC decreased with the addition of TCP compared with CP-Mg. Hydroxyapatite was formed on the surface of MMC samples after immersion in the SBF for 72 h but not on the surface of CP-Mg.

Dissolubility of Hydroxyapatlte Powder under Hydrothermal Condition

The dissolubility of hydroxyapatite(HA) in the hydrothermal solution was investigated in Mo-rey-type autoclave over a temperature range of 150 to 350℃ and the pH value range of 5 to 9. It is shown that the dissolubility of HA is determined as a function of temperature and time under a constant filling ratio of autoclave , and the temperature coefficient for the solubility of HA is positive. The equilibrium time attained in the hydrothermal solution is shortened with the increase of hydroihermal temperature, and the effect of temperature on the solubility is obviously stronger than that of pH value. The solubility data suggest that HA has higher dissolubility in the HA-H2 O system under the hydrothermal condition than that under the normal temperature-pressure.

Structural,morphological and photoluminescence characterizations of Sm^(3+) doped Y_(2)O_(3) nano-sized phosphors synthesized by ultrasound assisted sol-gel method

Nanosized 1 at% Sm^(3+)doped Y_(2)O_(3)powders were prepared by an ultrasound assisted sol-gel method.Y_(2)O_(3):Sm^(3+)powders crystallize in Y_(2)O_(3)pure cubic phase and XRD analysis shows that the as-used agitation protocol affects strongly the crystallite’s shape and mean size.The recorded emission spectra under λ_(em)=600 nm exhibit two absorption bands;the first one is assigned to O^(2-)→Sm^(3+)charge transfer state(CTS) with a maximum absorption at 223 nm,and the second is due to intraconfigurational transition 4f^(5)-4f^(5) of Sm^(3+) with a maximum absorption at 407 nm.The 223 and 407 nm transitions are attributed to characteristics intra-configurational transitions of Sm^(3+).All emission spectra are dominated by reddish/orange luminescence located at 606 nm and assigned to ^(4)G_(5/2)→^(6)H_(7/2) transition.It is found that the photoluminescence intensity of samples obtained under excitation at 407 nm is 60 times smaller than that obtained under 223 nm excitation.Decay time measurements of the ^(4)G_(5/2)→^(6)H_(7/2) luminescence transition indicate that decay time of nano-sized powder is significantly shorter than bulk material one.

Deposition of nano-crystalline tungsten carbide powders from gaseous WO_(2)(OH)_(2)

Lower WC grain sizes in the nanometer range have positive effects on the properties of hardmetals(e.g.,hardness),but the established production processes of WC are limited to grain sizes of about 150 nm.To produce WC powder with grain sizes in the lower nanometer range,an alternative WC production process based on the chemical vapor transport(CVT) reaction of WO_(3) and H_(2)O forming gaseous WO_(2)(OH)_(2) at about 1100 ℃,followed by a carburation reaction with H_(2)/CH_(4)-gas mixtures was investigated.The influences of different process parameters such as furnace temperature,humidity and gas flows were investigated to improve the process.With the right set of parameters the produced powder consisted mainly of agglomerated WC grains with a size of about 5 nm.Beside the common hexagonal WC phase,the cubic WC1-xphase was stabilized due to the small crystallite sizes.In addition,a thin layer of amorphous carbon was present on the powder surface due to the catalytic methane decomposition on the WC surface.The amount of oxidic and metallic residues in the product powder was minimized with the parameter optimization and the powder yield was increased up to about 50%.With further optimization of the process parameters and usage of improved flow breakers,the purity and yield of the product powder can be further improved.Since an application in the hardmetal section is not realistic at the moment,applications in the catalysis sector could be considered due to the small grain size and good catalytic activity of the cubic WC1-xphase.

钛合金羟基磷灰石骨植入复合材料的研究进展

钛及钛合金因具有高强度、低模量、优异的耐腐蚀性以及良好的生物相容性等优点,被广泛应用于生物医学领域,尤其是作为硬组织替换材料。然而,钛合金属于生物惰性材料,植入人体后难以与人骨实现良好的骨整合。以羟基磷灰石为代表的生物活性陶瓷能够诱导类骨磷灰石沉积和细胞攀附,但不能用于高承载部位。因此,为了改善植入体的生物活性,开发新型钛合金羟基磷灰石复合材料成为骨植入材料的研究热点。采用表面涂层法在钛合金表面制备羟基磷灰石涂层,能够显著改善基体的生物活性,但是存在两者结合强度不高、涂层易产生裂纹等缺点,需要从涂层成分、结构梯度化以及后处理等方面进行改进。粉末冶金技术能够使生物活性陶瓷与金属基体间实现冶金结合,却难以对材料组分分布和结构特征进行精确控制和调整。自然骨为由内部多孔松质骨和表面致密皮质骨组成的梯度结构,采用传统粉末冶金技术制备的骨科假体很难达到这一要求。增材制造技术可以个性化定制植入体,其逐层堆积的成形方式在梯度复合材料制备方面具有极大优势。近年来,研究人员尝试采用增材制造技术来实现植入体的成分复合化和结构梯度化,进一步调控其力学性能和生物学性能。本文总结了钛合金羟基磷灰石复合材料的研究现状,指出了目前研究中存在的问题,并进一步讨论了解决策略,最后提出了一种基于微滴喷射技术的钛合金羟基磷灰石多维梯度复合材料的增材制造方案,以期为开发功能复合的新型生物材料提供参考。

Microstructure and mechanical properties of Ti-6Al-4V-5% hydroxyapatite composite fabricated using electron beam powder bed fusion

A novel, Ti-6 Al-4 V(Ti64)/Hydroxyapatite(HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion(EPBF) additive manufacturing(AM): specifically, the commercial electron beam melting(EBM?) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell(model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm^3, and corresponding Young's moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ~3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. Both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, EPBF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography(OM) and scanning electron microscopy(SEM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha(hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ~5 μm in the EPBF-fabricated Ti64 to ~1.1 m for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 m. This work highlights the use of EPBF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors' knowledge has not been reported before. The results also illustrate the prospects not only for fabricating specialized, novel composite bone replacement scaffolds and implants, through the combination of Ti64 and HA, but also prospects for producing a variety of related metal/ceramic composites using EPBF AM.

Synthesis and Characterization of Nano-hydroxyapatite Powder Using Wet Chemical Precipitation Reaction

Hydroxyapatite （HA） nano-powder was synthesized via wet chemical technique in a used precipitation reaction, in which Ca（OH）2 and H3PO4 were used as precursors. Deionised water was used as a diluting media for the reaction and ammonia was used to adjust the pH. The synthetic HA nano-powder has some medical applications such as a coating material in orthopaedic implants and in dental. HA powder has been studied at different temperatures from 100 to 800 ℃ to achieve the stoichiometric Ca/P ratio 1.667. The optimum temperature was found to be 600 ℃. Above this temperature, the HA powder decomposed to CaO. The crystallite size of HA powder was found to be in the range of 8.47-24.47 nm. The crystallographic properties were evaluated by X-ray diffraction, Fourier transform infrared spectroscopy, energy dispersive X- ray spectroscopy and scanning electron microscopy. The results show that, high purity of nano-hydroxyapatite powders could be obtained at low temperatures, and the crystallinity, crystallite size and Ca/P ratio of the resulting nanoparticles were found to be dependent on the calcination temperature. When Ca/P ratio exceeded 1.75, formation of CaO phase was observed.

Promotional effect of silica on the combustion of nano-sized aluminum powder in carbon dioxide

This paper presents how the combustion performance of nano-sized aluminum(nAl)powder in carbon dioxide are affected by silica. The ignition and combustion performance of nAl powder with silica addition were studied by a high-temperature tube furnace. An s-type thermocouple and a high-speed motion acquisition instrument were performed to evaluate the ignition temperature, maximum combustion temperature, maximum change of rate of temperature, and combustion propagation speed. The combustion efficiency and combustion products were measured and analyzed by a gas-volumetric method and an X-ray diffraction. The results show that silica added into nAl powder can enhance its maximum combustion temperature and maximum change of rate of temperature, while its ignition temperature increases slightly. The nAl powders with addition of 6.00 wt.% and 12.00 wt.% silica present high combustion propagation speeds, especially for the latter, it has high combustion efficiency. The effect mechanism of silica on the combustion of nAl powder in carbon dioxide was discussed.

Ceramic membrane separation technique for washing nano-sized ceramic powder precursors

Washing using ceramic micro-filtration membranes was studied in the preparation of nano-sized TiO2 and A1203 powder precursors obtained by wet chemical methods. The key parameters for the washing process, such as operation pressure, cross-flow velocity, and slurry concentration, were examined and optimized. The shape and size of particles influenced the structure of the filter cake, leading to different permeation flux for different systems. The results demonstrated that washing using ceramic membranes is superior to the traditional plate-and-frame filtration and could be considered an advanced technique for ultra-fine powder preparation by wet-chemical method.