Preparation of calcium carbonate particles coated with titanium dioxide

The preparation of a new mineral composite material, calcium carbonate particles coated with titanium dioxide, was studied. The mechanism of the preparation process was proposed. The new mineral composite material was made by the mechanoehemieal method under the optimum condition that the mass ratio of calcium carbonate particles to titanium dioxide was 6.5：3.5. The mass ratios of two different types of titanium dioxide （anatase to rutile） and grinding media to grinded materials were 8：2 and 4：1 respectively, and the modified density was 60%. Under this condition, the new material was capable of forming after 120-min modification. The hiding power and oil absorption of this new material were 29.12 g/m^2 and 23.30%, respectively. The results show that the modification is based on surface hydroxylation. After coating with titanium dioxide, the hiding power of calcium carbonate can be improved greatly. The new mineral composite materials can be used as the substitute for titanium dioxide.

Enhancement of corona discharge induced wind generation with carbon nanotube and titanium dioxide decoration

Dip-coated double-wall carbon nanotubes(DWCNTs) and titanium dioxide(TiO2) sol have been prepared and smeared onto the tip of a conductive iron needle which serves as the corona discharge anode in a needle-cylinder corona system.Compared with the discharge electrode of a CNT-coated needle tip, great advancements have been achieved with the TiO_2/CNT-coated electrode, including higher discharge current, ionic wind velocity, and energy conversion efficiency,together with lower corona onset voltage and power consumption.Several parameters related to the discharge have been phenomenologically and mathematically studied for comparison.Thanks to the morphology reorientation of the CNT layer and the anti-oxidation of TiO_2, better performance of corona discharge induced wind generation of the TiO2/CNT-coated electrode system has been achieved.This novel decoration may provide better thoughts about the corona discharge application and wind generation.

Alloying elements characterization in a Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-1Nd titanium alloy by carbon addition

The effects of carbon addition (0.01wt%-0.43wt%) on a Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-1Nd (wt%) alloy with a bimodal microstructure were investigated. Electron probe microanalysis was carried out to examine the partitioning behavior of carbon and the relation of carbon content to the distributions of Al and Mo in the primary αp phase (α p) and β transformed structure (β). It was found that interstitial carbon is enriched in the α p phase and its content slightly reduces with the increase of the volume fraction of α p. The measurements of carbon content in the present alloy with an α p of 15vol% showed that the carbon content in the α p phase increases with the increment of carbon addition until a maximum but keeps almost constant in the β phase. The addition of carbon reduces the solubility of Al and Mo in the α p phase and leads to the increment of Mo partitioning to the β phase. When the carbon content is over 0.17wt% (0.67at%), carbide precipitation occurs in the matrix and its volume fraction is related to the volume fraction of α p which can be explained in term of the difference of carbon solubility in the α p and β phases.

Supercritical synthesis of platinum-modified titanium dioxide for solar fuel production from carbon dioxide

This paper investigates the properties of TiO2‐based photocatalysts synthesised under supercriticalconditions.Specifically,the characteristics of Pt dispersed on TiO2catalysts obtained in supercriticalCO2are discussed and compared with those of commercial TiO2.The photocatalytic activity of thesynthesised catalysts in the CO2photoreduction reaction to produce solar fuel is tested.The mainconclusion of the study is that photocatalysts with better or similar features,including high surfacearea,crystallisation degree,hydroxyl surface concentration,pore volume,absorbance in the visiblerange and methane production rate,to those of commercial TiO2may be produced for the reductionof CO2to fuel by synthesis in supercritical media.

Microstructural Evolution of Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-0.7Nd Titanium Alloy with Carbon Additions

The effect of carbon addition on microstructural evolution was studied in a near-α titanium alloy （Ti-5.6Al- 4.8Sn-2Zr-1Mo-0.35Si-0.7Nd）. It was found that flake and ribbon titanium carbides with a NaCl crystal structure formed in the as-cast alloys with carbon additions of over 0.17 wt pct. Flake carbide particles are the product of eutectic transformation and precipitate from the high-temperature β phase. The ribbon carbide particles are primary phases formed prior to the nucleation of any metallic phases. The as-cast alloys with carbide precipitation after heat-treatment at βt-30℃ followed by water quenching showed the spheroidization of α lamellae and partial dissolution of carbide particles. After annealing at βt＋15℃, carbide particles are mostly distributed at the grain boundary and spheroidized through mixed grain boundary plus bulk diffusions.

Indirect mineral carbonation of titanium-bearing blast furnace slag coupled with recovery of TiO_2 and Al_2O_3

Large quantities of CO2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO2 emission reduction and comprehensive utilization of the solid waste. This paper describes a novel route for indirect mineral carbonation of titanium-bearing blast furnace （TBBF） slag, in which the TBBF slag is roasted with recyclable （NH4）2SO4 （AS） at low temperatures and converted into the sulphates of various valuable metals, including calcium, magnesium, aluminium and titanium. High value added Ti-and Al-rich products can be obtained through stepwise precipitation of the leaching solution from the roasted slag. The NH3 produced during the roasting is used to capture CO2 from flue gases. The NH4HCO3 and （NH4）2CO3 thus obtained are used to carbonate the CaSO4-containing leaching residue and MgSO4-rich leaching solution, respectively. In this study, the process parameters and efficiency for the roasting, carbonation and Ti and Al recovery were investigated in detail. The results showed that the sulfation ratios of calcium, magnesium, titanium and aluminium reached 92.6%, 87% and 84.4%, respectively, after roasting at an AS-to-TBBF slag mass ratio of 2：1 and 350℃ for 2 h. The leaching solution was subjected to hydrolysis at 102℃ for 4 h with a Ti hydrolysis ratio of 95.7%and the purity of TiO2 in the calcined hydrolysate reached 98 wt%. 99.7% of aluminium in the Ti-depleted leaching solution was precipitated by using NH3. The carbonation products of Ca and Mg were CaCO3 and （NH4）2Mg（CO3）2·4H2O, respectively. The latter can be decomposed into MgCO3 at 100-200℃ with simultaneous recovery of the NH3 for reuse. In this process, approximately 82.1% of Ca and 84.2% of Mg in the TBBF slag were transformed into stable carbonates and the total CO2 sequestration capacity per ton of TBBF slag reached up to 239.7 kg. The TiO2 obtained can be used directly as an end product, while the Al-rich precipitate and the two carbonation products can act, respectively, as raw materials for electrolytic aluminium, cement and light magnesium carbonate production for the replacement of natural resources.

Study of Band Gap of Carbon Nanotube-Titanium Dioxide Heterostructures

The authors present a photoluminescence and UV （ultraviolet）-optical absorbance study on single walled carbon nanotubes CNTs （carbon nanotubes） and TiO2 mixtures. The authors observed variation of△ф = 0.6 eV in optical gap for micrometric anatase and 0.1 eV for nanometric rutile or anatase at a concentration of CNTs of about 1.5 weight %. The large difference in △ф is attributed to differences in dimensions of dioxide grains and in morphology of CNTs/Ti02 composites. Photoluminescence emission is drastically reduced and absorption in the UV range is increased at low CNT concentration for both anatase and rutile phases.

RTV silicone rubber composites reinforced with carbon nanotubes,titanium-di-oxide and their hybrid:Mechanical and piezoelectric actuation performance

The use of nanofillers with high surface area and extreme purity in polymer composite is an effective strategy to obtain high performance polymeric nanocomposites.Therefore,the effect of nanofillers such as carbon nanotubes(CNT),titanium dioxide(TiO_(2)),and their hybrid on rubber-based composites was studied.In this study,rubber nanocomposites were fabricated by using room temperature vulcanized(RTV)silicone rubber matrix and nanofillers(i.e.CNT,TiO_(2),and CNT-TiO_(2))through solution casting method.Here,the purity and surface area of CNT(purity:>96%and BET surface area:300 m2/g)and TiO_(2)(purity:>98%and BET surface area:165 m2/g)were estimated by field emission scanning electron microscopy/energy dispersive X-ray(FESEM-EDX)and adsorption isotherms.The mechanical properties of the rubber nanocomposites were enhanced by incorporating nanofillers.The compressive modulus was 2.18 MPa for unfilled composites and increased to 6.8 MPa(CNT),3.95 MPa(CNT-TiO_(2)),and 2.44 MPa(TiO_(2))at 5 phr,respectively.Similarly,the tensile strength was 0.54 MPa for unfilled composites and increased to 1.37 MPa(CNT),1.33 MPa(CNT-TiO_(2))and 0.61 MPa(TiO_(2))at 5 phr,respectively.Further,the actuation displacement was improved with increasing input voltage and it was 2 mm for CNT,1.6 mm for CNT-TiO_(2) hybrid and 0.5 mm for TiO_(2) at 10 kV.Moreover,a series of experiments show the potential application in piezoelectric actuation.

Effect of titanium content on the precipitation behavior of carbon-saturated molten pig iron

The use of iron ores bearing titanium as a raw material is an effective measure to prevent hearth erosion and prolong the life of a blast furnace. In this research, the effect of titanium content on the precipitation behaviors of high-melting phases of carbon-saturated molten pig iron were studied by confocal scanning laser microscopy. The results showed that, when the titanium content was less than 0.25 wt%,Fe_3C was precipitated as a single phase from the molten carbon-saturated iron. The growth rate of the precipitated Fe_3C crystals was very high, reaching 7387 μm^2/s. When the titanium content in the molten pig iron was greater than 0.47 wt%, TiC crystals precipitated first. The shape and size of the precipitated TiC crystals did not obviously change. After TiC was precipitated, the fluidity of the molten pig iron worsened. With a decrease in temperature, Fe_3C was also precipitated but the growth rate of Fe_3C was limited by the presence of the first precipitated TiC phase. The crystal size of the precipitated Fe_3C was much smaller than that of pure Fe_3C.

Evaluation of the osseointegration of dental implants coated with calcium carbonate:an animal study

In an attempt to overcome the limitations of titanium in dental and orthopaedic clinical applications, a new method has been developed to prepare calcium carbonate coatings on sandblasted and acid-etched （SA） titanium implants. The purpose of this study was to investigate the effect of calcium carbonate-SA （CC-SA） implants on osseointegration in vivo. The surfaces of SA and CC-SA implants were characterised for surface morphology and surface chemistry. Subsequently, these two kinds of implants were implanted in the femoral condyles of rabbits. The implants were retrieved and prepared for histological and histomorphometric evaluation 1, 2, 4, 8 and 12 weeks after implantation. Significantly higher values of bone-to-implant contact of the entire implant except the gap area （BIC_ALL） and the bone-to-implant contact of the gap area （BIC_GAP） were found in animals with the CC-SA implants than in those with the SA implants at 4 weeks. Higher values of total gap bone were found in those with the CC-SA implants than in those with the SA implants at 1, 2 and 4 weeks. In conclusion, the current findings demonstrate that the calcium carbonate coating can improve and accelerate the early ingrowth of bone and osseointegration at the early healine phase. This may reduce clinical healinE times and thus improve implant success rates.

Grafting Carbon Nanotubes on Titanium Surface for Osteoblast Cell Adhesion and Growth

Poly(ethylene glycol) (PEG) functionalized single-walled carbon nanotubes (SWCNTs) were covalently grafted on the titanium surface with the aim to provide a new platform for human osteoblast cells (HOCs) attachment. Water contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) results revealed that the PEG-functionalized SWCNTs were successfully grafted onto titanium surfaces. Cell viability and proliferation showed that the number of viable cells in culture medium increased with the incubation time for both titanium and SWCNT-modified titanium samples, although the SWCNT-modified titanium presented lower cell viability compared to titanium. Cell adhesion experiments suggested that there were no obvious differences in the number of cells adhered on the titanium and PEG-SWCNT-modified titanium, and the number of adhered cells increased with the culture time. To our best knowledge, for the first time the PEG functionalized SWCNTs were grafted on the titanium surface for human osteoblast cell adhesion and growth. The strategy introduced in the present study provides a new idea for the matrix preparation based on CNTs and titanium for the biological application and the new SWCNT-titanium platform has potential applications in implantable materials and bone tissue engineering.

Study of Dye Absorption in Carbon Nanotube-Titanium Dioxide Heterostructures

In this work, the authors present a study of dye absorption in TiO2 doped with CNTs （carbon nanotubes）. Absorption decreases exponentially with the increase of CNTs in the film, while morphological characterization, conducted by SEM （scanning electron microscope） and TEM （transmission electron microscope） microscopes, suggests that this behavior is strongly related to morphological structure of grown films. For CNTs amounts greater than 1%, the authors observe the formation of CNTs clusters randomly distribute on TiO2 bulk, which strongly reduces the film porosity quenching the dye absorption. Comparison with optical properties of CNT/TiO2 filmstudied in the previous work, suggest that the best level of doping is with 0.5% of CNTs. FTIR （Fourier transform infrared spectroscopy） measurements conducted on a series of pristine and doped samples clearly indicate the absence of change in allotropic species of TiO2, while AFM （atomic force microscope） analysis indicates that the sample roughness strongly changes with doping, preventing the dye adsorption. Finally, measurements of cell efficiency indicate an increase of 5% in cells with 0.5% of CNT doping and a decrease for greater values.

纺丝液配制对PI/TiO_(2)活性碳纳米纤维膜吸附性能的影响

以均苯四甲酸酐(PMDA)、4,4′-二氨基二苯醚(ODA)及纳米TiO_(2)为原料,采用静电纺丝及热酰亚胺化的方法制备聚酰亚胺/二氧化钛(PI/TiO_(2))复合纳米纤维膜,在高温下对PI/TiO_(2)复合纳米纤维膜进行活化处理,通过正交试验研究了PMDA与ODA摩尔比、纳米TiO_(2)含量及纺丝液含量对PI/TiO_(2)活性碳纳米纤维膜吸附性能的影响。结果表明:PMDA与ODA摩尔比为1.03∶1、TiO_(2)质量分数为3%、纺丝液质量分数为22%时,活性碳纳米纤维薄膜的吸附性能最佳。

秸秆水热碳化液修饰二氧化钛去除农村生活污水尾水中抗生素的动力学特征研究

为探究秸秆水热碳化液修饰二氧化钛纳米球(SHCS&TiO_(2))去除抗生素的动力学特征,以实际农村生活污水尾水为目标处理水体,以磺胺嘧啶和红霉素为典型目标污染物,采用时间梯度实验研究和动力学模拟进行分析。结果表明:1)SHCS&TiO_(2)去除两种抗生素的动力学特征有明显差异。去除磺胺嘧啶反应主要发生在前10 min,去除速率为2.11~2.37 mg/(L·min),最终去除率为72.6%~89.5%。去除红霉素反应主要发生在0~20、120~240 min,去除速率分别为1.65~2.34、0.32~0.42 mg/(L·min),最终去除率达到100.0%。2)Behnajady-Modirshahla-Ghanbary反应动力学模型模拟结果最佳。3)去除机制是吸附和催化共同作用,且催化起主要作用。

基于钛质铆钉的低碳钢/钛电阻单元焊接接头的组织与性能

以钛质铆钉作为单元件对2 mm厚的钛和Q235低碳钢板进行电阻单元焊。利用扫描电镜观察接头中各区域的微观组织结构,分析了焊接参数对接头抗剪载荷和十字抗拉载荷的影响。结果表明:低碳钢/钛电阻单元焊接接头的抗剪载荷与十字抗拉载荷随焊接电流、焊接时间的增加而呈现先增大后减小的趋势。当铆钉腿径为8 mm、焊接时间为300 ms、焊接电流为12 kA时,接头的抗剪载荷与十字抗拉载荷分别为11.26和7.39 kN。采用电阻单元焊焊接低碳钢/钛时,铆钉的腿径在4~8 mm范围内,所用铆钉的腿径越大,适焊窗口越宽。

TiO_(2)催化剂催化CO_(2)还原的研究进展

碳排放量的不断增加导致环境问题日益严重,寻找解决途径已成为全球共同关注的焦点。通过光催化、电催化还原CO_(2)可以将其转化为有用的燃料或化学品。TiO_(2)因具有化学性质稳定、催化活性高、价格低廉、无毒无污染等优点而备受青睐。综述了光催化CO_(2)还原和电催化CO_(2)还原的反应机理;阐述了TiO_(2)在光催化和电催化还原CO_(2)中的应用和优势、不同表面改性技术对TiO_(2)的催化性能的影响以及TiO_(2)的形貌对CO_(2)还原催化活性和选择性的影响;对TiO_(2)基催化剂催化性能的提升方法进行了讨论。综述为可持续碳转化提供科学基础,并有助于进一步实验和理论探索TiO_(2)的作用机理。

激光刻蚀缺陷增强Pt/TiO_(2)光催化还原CO_(2)性能的实验研究

针对二氧化钛(TiO_(2))在光催化反应中光响应能力差、光生载流子易复合等问题,采用激光刻蚀方法对锐钛矿TiO_(2)进行改性,并对其由于激光刻蚀造成的结构和性质变化,以及Pt负载后的金属-载体相互作用特征进行研究。实验结果表明:激光刻蚀导致锐钛矿TiO_(2)的晶粒尺寸增大,形成金红石相,并在TiO_(2)中产生了氧空位(O_(v))和Ti^(3+)缺陷,导致其带隙缩小以及对可见光的响应增强;与原始TiO_(2)中存在的缺陷相比,激光刻蚀诱导的缺陷更稳定,还原性更强,因而以缺陷型TiO_(2)作为载体制备的缺陷型Pt/TiO_(2)催化剂中的金属-载体相互作用也更剧烈,具有更强的电子转移能力和载流子分离性能,在光催化还原二氧化碳(CO_(2))过程中表现出极佳的反应活性和产物选择性。该结果可为激光刻蚀催化剂载体及催化剂在光催化中的材料特性和催化应用研究提供理论支持。

二氧化钛/多孔碳纳米纤维复合材料的制备及其光催化性能

为实现纳米二氧化钛(TiO_(2))的回收和重复使用,采用静电纺丝、高温煅烧和酸溶技术制备了多孔碳纳米纤维(PCNF),随后使用二次形核法将锐钛矿相TiO_(2)负载到其表面,得到具有光催化活性的TiO_(2)/PCNF复合材料。通过扫描电子显微镜、X射线衍射仪、X射线光电子能谱仪、紫外-可见漫反射光谱仪等表征了TiO_(2)/PCNF复合材料的形貌结构、成分和光吸收性能,并测试了其对降解亚甲基蓝(MB)溶液的光催化性能。结果显示:复合材料的比表面积高达331.9 m^(2)/g,光照30 min后对MB溶液(5 mg/L)的去除率为98.6%,光照60 min后对MB溶液的去除率可达99.6%,均高于同等TiO_(2)含量的对比组;重复使用5次后,其对MB溶液的去除率仍然保持在95.0%;PCNF是一种性能优异的光催化载体材料,它不仅能够实现对纳米TiO_(2)的固定和回收,而且能提高TiO_(2)的光催化性能。

电感耦合等离子体质谱(ICP-MS)法测定锆钛矿中的铪

锆钛矿中存在耐高温的锆、钛化合物,铪以类质同象进入锆矿物中,准确测定锆钛矿中的铪对选矿研究、矿物综合利用及工业生产有重要作用。通过考察锆钛矿成分及熔融方法,以碳酸钠-硼砂高温熔融锆钛矿,以178 Hf为分析同位素及185 Re为内标,使用电感耦合等离子体质谱法测定锆钛矿中含量不均的铪。结果表明,碳酸钠-硼砂高温熔融效果最好,可完全溶解耐高温难分解的锆钛矿,当碳酸钠-硼砂质量配比为2∶1时熔融效果最佳。ICP-MS蠕动泵转速为45 r/min、雾化气流量为1.06 L/min时雾化效率最优。在选定的实验条件下,HfO_(2)质谱强度与质量浓度在0.01~250 ng/mL呈良好的线性关系,相关系数为0.9997,背景等效浓度为0.029 ng/mL,方法检出限为0.0032 ng/mL。按实验方法对中国国家标准物质中的HfO_(2)进行测定,测定值与认定值一致,相对标准偏差在1.6%~3.2%。按实验方法对锆钛矿样品中的HfO_(2)进行测定并进行加标回收实验,测定结果的相对标准偏差(RSD,n=9)为0.90%~3.4%,加标回收率在96.0%~106%,满足国家地质矿产行业标准DZ/T 0130—2006的要求。