Synthesis and Structural Characterization of Hydroxyapatite-Wollastonite Biocomposites, Produced by an Alternative Sol-Gel Route

Hydroxyapatite is a type of calcium phosphate-based material with great interest for biomedical applications, due to the chemical similarity between this material and the mineral part of human bone. However, synthetic hydroxyapatite is essentially brittle;the practice indicates that the use of hydroxyapatite without additives for implant production is not efficient, due to its low strength parameters. In the present work, biocomposites of hydroxyapatite-wollastonite were synthesized by an alternative sol-gel route, using calcium nitrate and ammonium phosphate as precursors of hydroxyapatite, and high purity natural wollastonite was added in ratios of 20, 50 and 80 percent by weight immersed in aqueous medium. Formation of hydroxyapatite occurs at a relatively low temperature of about 350?C, while the wollastonite remains unreacted. After that, these biocomposites were sintered at 1200?C for 5 h to produce dense materials. The characterization techniques demonstrated the presence of hydroxyapatite and wollastonite as unique phases in all products.

Chemical Kinetic Aspects of Solid State Reaction Producing Wollastonite from Rice Husk Silica and Limestone

An industrial mineral wollastonite (CaSiO3) was produced under solid state conditions from rice husk silica and limestone. Reaction was carried out at 900'C to 1300'C for 1 h. The product batches were subjected to XRD and chemical analysis techniques specific for wollastonite. Mole fractions of different product batches were calculated on the basis of accumulated data to study the kinetics. Specific rate constants and reaction rate were also found out. Various probable models of mechanism for reaction were considered and testified with the laid down criterion for suggesting the suitable one. The resulting data were treated with Arrhenius equation as well and activation energy was calculated--therefrom. In addition to finding it's value from the slope of Arrhenius curve, an alternate method was also applied for this purpose. Both of the values were observed to be comparable. The activation energy required for performed reaction was found to be almost one third of that reported for synthesizing CaSiO3 by using quartz. This referred to the economical preparation of wollastonite by using rice husk as a source of silica instead of quartz.

Immobilization of RGD Peptide onto the Surface of Apatite-Wollastonite Ceramic for Enhanced Osteoblast Adhesion and Bone Regeneration

The arginine-glycine-aspartic （RGD） acid peptide was grafted to the surface of apatitewollastonite （AW） ceramic in an effort to improve its cell adhesion, proliferation and osteoinduction. RGD peptide was covalently immobilized onto the surface of AW ceramic via the synthetic cross linker AA.PTS-E and 1-ethyl-3-（3-dimethylaminopropyl）carbodiimide （EDC）. The modified surfaces were characterized by attenuated total reflectance Fourier transform infrared spectroscopy （ATR-FTIR） and X-ray photoelectron spectroscopy （XPS）. The chemical analysis indicated that RGD peptide had been immobilized onto the AW surface successfully. The growth of osteoblast-like cells （MG63） showed that modifying the AW surface with RGD peptide enhanced the cell adhesion and proliferation. And the histological evaluation of RGD-AW showed that the bone regeneration and remodeling process were significantly enhanced compared to the original AW ceramics after 2, 4 and 8 weeks implantation in rabbit＇s femoral condyles.

New Discovery of Shizhushan Superlarge Wollastonite Deposit in Xinyu City, Jiangxi Province

Objective The Mengshan area of the Xinyu City, Jiangxi Province is an important wollastonite production base in China. As early as the 90s of the 20th century, more than ten medium to small-sized wollastonite deposits, such as the Yueguangshan and Caofangmiao Deposits were discovered in the outer contact zone of the Mengshan rock mass. After that, no more progress was achieved in wollastonite prospection. In 2016, the project funded by the Geological Prospecting Fund of Jiangxi Province made significant breakthroughs in the ＂General Survey of the Shizhushan Wollastonite Ore in the Yushui District and Zhangmuqiao Wollastonite Ore in Shanggao County, Xinyu City, Jiangxi Province＂ in the Mengshan area. The new discovered Shizhushan Wollastonite Deposit has a scale of 50 million tons and its resources scale far exceeds that of the Seeleys Bay Wollastonite Deposit discovered in Canada.

In vitro Evaluation with 5SBF of Alloy ASTM F75 Thermally Treated with Wollastonite

Samples of a cobalt-based alloy that underwent a surface treatment were evaluated. The samples, which were obtained by casting alloy ASTM F 75, were ground and polished on one side until a mirror finish was obtained. The samples were encapsulated in wollastonite （W） using uniaxial pressure, treated at 1 220 ~C for 1 h and subsequently tempered in water. The characterisation of the sample indicated that part of the ceramic encapsulating material was mechanically incorporated on the metallic surface by growth of the oxide layer of the alloy. After thermal treatment, a series of specimens were submerged in a solution with 5-fold simulated body fluid （5SBF） for 3, 5 and 21 days. Characterisation by scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD） indicated nucleation and growth of a homogenous layer of apatite, beginning on the third day when the sample was submerged.

STUDY ON SOLUTION CHEMISTRY BETWEEN TANNIC ACID AND THE FLOTATION PULP OF WOLLASTONITE AND DIOPSIDE

The mechanisms of interaction between tannic acid and calcium ions either added externally to or inherently present in the (?)olution ( dissociated from mineral surface ) , are studied by the use of Inductively Coupled Plasma Atomic Emission Spectroscopy ( ICP-AES ) , Ultraviolet Spectroscopy (UV). It is found that wollastonite has a high solubility in the concentration of calcium ions, calcium ions are able to interact with tannic acid.

EFFECT OF SOLUTION CHEMISTRY ON THE FLOTATION SEPARATION OF WOLLASTONITE FROM QUARTZ

This paper deals with the flotation separation of wollas-tonite from quartz by using Na-oleate as a collector and metallic ion as an activator. The reasons why wollastonite is difficult to separate from quartz using Na-oleate as a collector have been studied. It is found that quartz does not float well in a mixture of wollastonite and quartz because of the solution chemistry effect in a wollastonite suspension. The compositions of the wollastonite suspensions have been studied, and the?potential of the two minerals have been determined to explain the solution chemistry effects on the flotation of the respective minerals.

Reciprocity Effect between Silicate Bacteria and Wollastonite

This paper studied the reciprocity effect between wollastonite and a strain silicate bacterium from purple soil. We analyzed the changes of pH value, glucose (GLU) residual concentration, electrolyte and Mn, Si, Fe etc. in the culture liquid with wollastonite after 48 h. The results show that the GLU wastage of silicate bacteria with wollastonite is 2.5 times of the bacterial contrast. It showed wollastonite could obviously accelerate silicate bacteria growth, but bacterial cell broken and distorted badly have been found by SEM analysis. The solubilization of silicate bacteria to Si element of wollastonite reached above 10 times. At the same time, three apices in FTIR of wollastonite (898 cm-1, 925 cm-1, 962 cm-1) descended obviously after the action of silicate bacteria, which shows that a great deal of Si has dissolved out. So we can get that wollastonite has remarkable effect to the growth of silicate bacteria and silicate bacteria has obvious solubilization to Si of wollastonite.

STUDY ON THE GRAVITATION SEPARATION OF SKARN-TYPE WOLLASTONITE ORE FOR PURIFICATION

This paper introduces the common paragenetic minerals of skarn-type wollastonite ore and its principle of gravitation separation for purification. Through the separation experiment of concentrating table on the wollastonite ore from Xiaojipu Wollastonite Mine of Hubei province, the product has reached the reguirement of wollastonite powder used as the ceramic raw material.

STUDIES ON THE APPLICATION OF TOWER MILL IN THE PRODUCTION OF ULTRAFINE WOLLASTONITE

The feasibilities of ultrafine fvollastonits prnvder have been analysed based on joint considerations of satisfying product size re-quiremet, presenting the needlelike wollastonite structure, maintaining an easy operation, stable performance and simplified flowsheet, etc. Opti-mum operating conditions have been established through, systematic reseach-es on the bases of product requirements. Modern analytical technique such as light-transmission particle sizing and scanning electron spectroscopy have been used to determine the size and morphology of the product. It is found that the meedelelike structure can be preserved even dawn to the ul-trafine range by using the toiver mill. The torver mill is easy to operate, has stable performances, and can be used in open-circuit to produce re-quired products without needing for a classifier.

SURFACE CHEMICAL CHARACTERISTICS AND FLOATION SEPARATION OF WOLLASTONITE AND GARNET

In order to nealize the efficient floatation separation of garnet and uiollastonite , the authors studied the surface chemical charac-teristics and various floatation behaviour of the two minerals?developed acidic combination depressant FDi and introduced sodium oleate j FeCls and FDi as the flotation agent, they achieved success. In the experimental re-search on the artificiallymixed ores separation, the recovery and concentra-tion grade of the two minerals ivere both over 92% and 95% respectively. At the same time , it was found that the chemical absorption form of iron oleate presented bridge and chelating patterns on the surfaces of garnet and wollastonite activated by Fe3+.

Evaluation on Fabrication and Properties of Composite Polyurethane Coatings with Wollastonite Partially Substituting for Rutile Titanium Dioxide

This study aims to prepare a composite polyurethane coating through a facile synthesis process. Titanium dioxide, which is a component of the prepared hydroxyl acrylic resin polyurethane varnish, was partially substituted by wollastonite, and an optimal substitution ratio was obtained. Analyses based on scanning electron microscope, powder X-ray diffraction, and Raman scattering measurements demonstrated that the addition of wollastonite caused nearly no change in the basic structure of the coating. Coating with a substitution ratio of 25% showed high thermal stability, good cover effect, considerable moisture-proof and water resistance ability, great acidic and basic resistance, and improved performance and hardness in performance tests. Furthermore, the production cost was reduced significantly at this substitution ratio.

Evaluation of Bioactive Properties of α and β Wollastonite Bioceramics Soaked in a Simulated Body Fluid

Dense natural wollastonite bioceramics (CaSiO3) were prepared by a sintering method, varying the pressing load and sintering temperature, in order to obtain different phases of wollastonite, and different physical properties in the materials. The products were characterized by TGA-DTA, XRD, FT-IR, SEM-EDS, TEM and XPS techniques. The results indicate the presence of two polymorphic phases of wollastonite, the β-wollastonite and α-wollastonite with a transition temperature of the β phase to α phase at approximately 1250℃. These materials were soaked in a simulated body fluid (SBF) during 1, 2 and 3 weeks, to study their solubility and bioactivity. The effect of different wollastonite phases on the solubility of Ca and Si, as well as the capacity of producing layers of “newly formed apatite” on the surfaces of these materials in SBF solution were analyzed.

Raman Spectroscopy Analysis of Wollastonite/Tricalcium Phosphate Glass-Ceramics after Implantation in Critical Bone Defect in Rats

In this work wollastonite/tricalcium phosphate (W/TCP) glass-ceramics with three W/TCP weight ratios (20/80;60/40 and 80/20) were implanted in rat calvaria and the modifications taking place during implantation were studied by Raman spectroscopy. The experimental glass-ceramics were composed of different contents of βW, αW, βTCP, αTCP, and glassy phases. Materials were implanted for 7-, 15-, 45- and 120-day periods after which the implanted materials were recovered and analyzed by FT-Raman spectroscopy. The results suggested that the αW phase reabsorbs fast during implantation in the glass-ceramics 60/40 and 80/20, whereas βTCP and αTCP glass-ceramic are gradually attenuated and replaced by biological apatite-like bands. In the glass-ceramic 20/80, the bands related to the βTCP phase remained unvaried in all analyzed periods. New bands associated with the deposition of collagenous material appeared during implantation for all 60/40 and 80/20 glass-ceramics experimental groups, but important differences in intensities between both groups. The spectra corresponding to implants of 60/40 glass-ceramic at the 120-day period were very similar to those of the control group (normal cortical bone), with regards to Raman shifts and intensities, as well as in the FWHM value of the 962 cm-1 apatite band (ν1 PO4 in hydroxyapatite), evidencing that apatite deposited at the implant site has the same crystallinity than biological apatite in normal bone mineral. The glass-ceramic 20/80 behaved just as an osteoconductive filling material, while glass-ceramics 60/40 and 80/20 were able to induce deposition of organic matrix mineralized new tissue. The 60/40 glass-ceramic showed the best performance and the most similar Raman spectrum to normal cortical bone.

相容剂对PBAT/硅灰石复合材料性能的影响

以生物降解塑料聚对苯二甲酸己二酸丁二醇酯(PBAT)为聚合物基体,硅灰石(WT)作为填料,以2,3-甲基丙烯酸环氧丙酯(ADR)作为相容剂,通过熔融挤出制备得到PBAT/硅灰石复合材料,考察了相容剂ADR对PBAT/硅灰石复合材料结构及性能的影响。研究结果表明,相容剂可改善硅灰石在PBAT基体中的分散性,增强界面相互作用,提高复合材料的力学性能和热稳定性。

硅灰石与金红石型TiO_(2)颗粒复合及其颜料性能

对通过干法研磨方式进行硅灰石和金红石型TiO_(2)(R-TiO_(2))颗粒复合及其颜料性能和颗粒微观结构进行了研究,对所制备复合颜料性能、结构和复合作用性质进行了表征。结果表明,硅灰石/R-TiO_(2)复合颜料具有和钛白粉相当的颜料性能,含TiO_(2)40%复合颜料遮盖力为14.04g/m^(2),达到纯TiO_(2)的90.10%;硅灰石/R-TiO_(2)复合颜料对紫外线吸收强烈,并与R-TiO_(2)一致。硅灰石/R-TiO_(2)复合颜料以TiO_(2)在硅灰石表面均匀、牢固包覆为特征所形成,硅灰石与TiO_(2)通过颗粒表面脱羟基反应实现结合。

方解石型硅灰石可选性试验研究

方解石型硅灰石因其中含有方解石、石英、白云石等杂质,附加值不高,为高效利用方解石型硅灰石矿,采用浮选方法对其进行降杂处理。结果表明,磨矿细度-0.074 mm占60%,捕收剂氧化石蜡皂用量为300 g/t,浮选脱去方解石等杂质,再在捕收剂十二胺用量为60 g/t的条件下浮选除去石英杂质,得到精矿品位为96.70%,回收率达到88.58%的硅灰石精矿。

针状填料对聚乙烯烟密度的影响

研究了针状填料对PE复合材料烟密度的影响。材料烟密度测试结果表明,单独添加50wt%的ATH时,PE复合材料的有焰最大比光密度为125.1,无焰最大比光密度为373.9。与单独添加ATH相比,当同时添加42.5wt%的ATH和7.5wt%的针状硅灰石时,PE复合材料有焰最大比光密度从125.1降低到86.6;无焰最大比光密度从373.9降低到293.5。而当同时添加42.5wt%的ATH和7.5wt%的球形碳酸钙时,PE复合材料有焰最大比光密度为163.5;无焰最大比光密度为411.2。针状的硅灰石提升了复合材料的抑烟性能。通过锥形量热和炭层分析发现,硅灰石提高了PE复合材料的炭层完整性和连续性,连续致密的炭层发挥了优异的覆盖隔绝作用,抑制了燃烧热的释放和烟雾的逸出,从而提高了PE复合材料的抑烟性能。

硅灰石纤维增强页岩气固井水泥力学性能及影响研究

页岩气作为一种清洁、高效的非常规能源,开采过程中需要进行压裂作业,对固井水泥石提出了较高的韧性要求,本文研究了硅灰石纤维增强页岩气固井水泥力学性能和微观结构。试验结果表明:页岩气固井水泥具备更加优异的抗压强度和抗折强度。掺杂一定量的硅灰石纤维有利于水泥石力学性能的提高,使水泥石具备更好的韧性,硅灰石纤维的最佳掺量为5%~10%。通过微观测试分析发现,硅灰石纤维增强水泥石力学性能一方面是因为硅灰石纤维参与水化反应,消耗氢氧化钙形成水化硅酸钙,提高其与水泥基体的粘结力;另一方面是因为当水泥石受到外力而产生裂纹时,硅灰石纤维能够使得裂纹发生偏转阻碍裂纹的拓展,进而起到增韧止裂的作用。

新型膨胀型防火涂层的耐火性能研究

对用于钢结构的膨胀型防火涂料进行了试验研究。该涂料主要由硅灰石和膨润土填料构成,试验样品包括5种配方共计10个试样,每种配方研磨时间分别为1~2min。依据《建筑设计防火规范》进行了耐火试验,记录了基材的温度。采用电子显微镜对残余炭成分及残炭量进行了分析。利用X射线光电子能谱(XPS)分析了炭的结合能和元素组成,X射线衍射(XRD)分析表明残余炭中含有硼酸铝和硼磷酸盐,并通过傅立叶变换红外吸收光谱(FTIR)的官能团分析进行了确认。场发射扫描电镜(FESEM)和高分辨透射电镜(HRTEM)分析表明,炭形态与硅灰石颗粒有关。热裂解–气相色谱/质谱(Py–GC/MS)结果显示,涂料燃烧产生的有害气体产物浓度更低,对坏境的破坏更小。