透明片状磷酸氢钙晶体的制备

<正> 荧光灯是依靠紫外线激发灯管内壁所涂的一层荧光粉而发光。因此荧光粉的质量好、坏将直接影响到荧光灯的质量。荧光灯常用荧光粉是卤磷酸钙荧光粉(下称卤粉)。卤粉自1942年发明以来,至今已有40多年的历史。经过不断的改进和完善制备工艺,质量得     

提高卤磷酸钙荧光粉抗光衰性能的有效方法

为了提高卤磷酸钙荧光粉抗光衰性能，在荧光粉成品水洗或酸洗过程中添加微量Ｓｂ２Ｏ３，经一系列试验及试生产，发现能有效地提高卤磷酸钙荧光粉抗光衰性能。     

红色荧光粉Sr1．5x＋y（VO4）x（MoO4）y：Eu^3＋溶胶-凝胶法制备；表征及其性能研究

本文对新型红色荧光粉Sr1．5x＋y（VO4）x（MoO4）y：Eu^3＋的合成及其发光性能进行了探索。通过TG—DTG，LS，XRD，TEM测试和分析，对荧光粉前驱体的分解过程，以及样品的发光性能，晶型结构，颗粒的形貌进行了研究。实验结果表明：该样品在700℃时晶体开始形成；室温下，在466nm处激发，在617nm处得到较强的红光发射。且发光强度受到钒酸盐和钼酸盐的配比用量，煅烧时间，络合剂的用量，Eu^3＋浓度的影响。采用溶胶-凝胶法得到的粉体颗粒分布均匀，尺寸大小在200hm左右。所以，Sr1．5x＋y（VO4）x（MoO4）y：Eu^3＋作为一种用于WLED的新型红色荧光粉，具有较好的应用前景。     

MgAl2O4:Ce荧光粉辐照合成及发光机理研究

通过伽马射线辐照辅助聚丙烯酰胺凝胶法合成了MgAl₂O₄和MgAl₂O₄:Ce荧光粉。通过X射线粉末衍射仪（XRD）、透射电子显微镜（TEM）、紫外可见分光光度计和荧光分光光度计研究了MgAl₂O₄:Ce荧光粉的晶体结构、表面形貌、光学性质和发光性质;基于实验所获得的结果,分析了纳米级MgAl₂O₄:Ce荧光粉的发光机理。实验结果表明:采用伽马射线辐照辅助聚丙烯酰胺凝胶法制备纯相MgAl₂O₄和MgAl₂O₄:Ce荧光粉的结晶温度要比传统聚丙烯酰胺凝胶法低100 ℃左右;MgAl₂O₄:Ce荧光粉的平均颗粒尺寸为14 nm,Ce离子掺杂后导致样品颗粒细化;Ce离子的掺入,降低了MgAl₂O₄的能带值,改善了其颜色性质和发光性质;当采用275 nm的光去激发MgAl₂O₄:Ce荧光粉时,获得了425 nm和464 nm的蓝光发射。通过能量传递原理分析认为,杂质缺陷（Ce³⁺）在整个发光过程中扮演了重要角色。MgAl₂O₄:Ce作为一种抗辐射能力强的荧光粉,在空间照明领域具有很好的应用前景。     

等离子喷涂-水热处理制备二氧化钛-羟基磷灰石复合涂层

为克服等离子喷涂羟基磷灰石生物涂层在结合强度和成分上的缺点，通过在钛合金基体上等离子喷涂二水磷酸氢钙和二氧化钻(锐钛矿型)复合粉末，并后续水热处理，制备了二氧化钛—羟基磷灰石复合涂层。结果表明：二水磷酸氢钙和二氧化钛复合粉末的等离子喷涂涂层由CaHPO4,Ca2P2O7,Ca3(PO4)2，非晶磷酸钙和二氧化钛组成。水热处理涂层由羟基磷灰石和二氧化钛组成，升高水热处理温度可提高涂层中羟基磷灰石的结晶性。随着原始粉中二氧化钛加入量的增加，喷涂涂层中磷酸钙的含量和水热处理涂层中羟基磷灰石的含量减少，羟基磷灰石的晶体形貌从细针状变为小颗粒状，喷涂涂层和水热处理涂层的结合强度也随之升高。当二氧化钛的质量分数为60％，水热处理涂层的结合强度可达17MPa。     

发光化学镍复合镀层(英文)

在90℃下,采用含有25 g/L硫酸镍,20 g/L次磷酸钠、35 g/L柠檬酸钠、0～6 g/t,卤磷酸钙和15 g/t.硫酸铵的镀液(pH 5.5),制备了基于卤磷酸钙的发光化学镍复合镀层.研究了镀液pH对复合镀层的沉积速率及卤磷酸钙含量的影响.采用硬度测量、磨损测试、腐蚀试验、紫外光谱,扫描电镜和X射线衍射对复合镀层进行了表征.在最佳卤磷酸钙质量浓度(4 g/L)下所得的复合镀层含77.59%(质量分数)镍、7.58%(质量分数)磷和14.83%(质量分数)卤磷酸钙.由于卤磷酸钙是硬质粒子,随着其嵌入量的增多,复合镀层的硬度增大.在存在卤磷酸钙的条件下,化学镍复合镀层的耐磨和耐蚀性能均显著提高.     

CuAl2O4和CuAl2O4：Cr荧光粉的合成及发光机理研究

采用温和的溶胶-凝胶法以酒石酸作为螯合剂制备了铝酸铜（CuAl₂O₄）和CuAl₂O₄：Cr荧光粉。X射线粉末衍射结果表明,铝酸铜干凝胶在800 ℃烧结获得了纯的立方相的铝酸铜,而CuAl₂O₄：Cr干凝胶烧结后为铝酸铜和三氧化二铬的混合相。元素组分与电荷态分析表明,铝酸铜和CuAl₂O₄：Cr荧光粉中不含其他杂质元素,且存在少量的吸附氧。扫描电镜分析表明,铝酸铜和CuAl₂O₄：Cr荧光粉的颗粒形状近似呈球形,每个大的颗粒由很多细小的晶粒组成,CuAl₂O₄：Cr荧光粉颗粒间的团聚现象较为明显。光学性质分析发现,CuAl₂O₄：Cr荧光粉颗粒间明显的团聚现象导致它的光学带隙值比铝酸铜小。采用255 nm的光激发CuAl₂O₄：Cr荧光粉,在690 nm处获得了一个强的荧光发射峰,主要归因于Cr³⁺中²E_g→⁴A_2g的跃迁。     

小粒径BaMgAl_(10)O_(17):Eu~(2+)荧光粉的合成机理

使用化学沉淀法制备细粒径、分散性好的圆饼状α-Al2O3粉体,并以此为原料,通过高温固相法制备粒径细小、颗粒形貌规则的高性能BaMgAl10O17:Eu2+(BAM)荧光粉,重点研究合成过程中的物相转变及颗粒生长等过程。结果表明:氧化铝原料颗粒对最终BAM荧光粉的颗粒形貌和粒径起到重要作用,经过1500℃煅烧2h后生成的BAM仍基本维持原α-Al2O3颗粒的圆饼状外形,颗粒粒径仍为2.5μm左右且分散性良好。高温固相法制备BAM荧光粉的过程中,1000℃时,首先在α-Al2O3颗粒表面反应形成一层BaAl2O4相,当温度继续升高,MgO参与反应,通过BaAl2O4层进行传质过程,并最后完全转变为BaMgAl10O17相。发光性能测试表明:使用自制氧化铝制备的BAM荧光粉具有良好的发光特性,其发射光谱峰的强度和半峰宽与使用商用氧化铝原料所制得的荧光粉的相当。     

氢氧化钙-磷酸体系在沉淀法合成羟基磷灰石过程中原料粒度的影响

采用化学沉淀法,分别以3种不同颗粒尺寸的氢氧化钙[Ca(OH)2]与磷酸(H3PO4)反应制备羟基磷灰石(hydroxyapatite,HA)粉末,研究了原料粒度对合成HA的影响.测定了合成过程中溶液的pH值和不同反应时间内合成产物的摩尔比n(Ca)/n(P),并表征了所得粉末的组成、颗粒形貌和粒度分布.研究表明:在采用粒度为57～88 μm的中等尺寸的原料时,合成过程中,溶液大部分时间处于较高的碱性范围,得到的HA粉末的纯度高、颗粒尺寸分布范围较窄.采用较大尺寸的原料时,溶液的碱性较低,合成的HA粉末中存在磷酸钙β-Ca3(PO4)2(β-TCP)和氧化钙(CaO)且尺寸分布范围较宽.采用较小尺寸原料时,HA粉末存在较严重的团聚现象,团聚体尺寸较大.Ca(OH)2-H3PO4体系用化学沉淀法制备HA粉末时,Ca(OH)2颗粒尺寸是影响合成过程的重要因素之一.     

小粒径氧化铝粉的制备及其在荧光粉合成中的应用

在碳酸铝铵法制备氧化铝工艺的基础上,通过控制沉淀条件及加入晶体生长促进剂等方法,有效控制了颗粒的大小和形貌,改善了氧化铝的结晶;并使用自制的α-Al2O3粉为原料合成了铝酸盐荧光粉。结果表明:促进剂对α-Al2O3颗粒的大小和形貌影响很大,适量加入可以获得粒径1～2μm,厚度0.2～0.3μm的规则外形α-Al2O3颗粒,且分散性良好;该α-Al2O3粉反应活性高,以该α-Al2O3粉为主原料无需添加助熔剂即可通过高温固相反应法合成物相纯净、结晶良好、且粒径细小的铝酸盐荧光粉。     

荧光灯制灯工艺对卤粉性能影响的研究

制作荧光灯时,灯用卤粉先后经过球磨、烤管、排气(或释汞)、老炼等工艺程序。这些工艺对卤粉发光性能的影响,主要在球磨、烤管工艺对卤粉发光性能的影响作过研究和报导。我国各制灯厂的制灯工艺尚未建立起严格的统一规范,因而同一性能的灯用卤粉在不同制灯厂的制灯水平差异较大,为此有必要就制灯工艺对卤粉发光性能的影响开展系统工作,以搞清不同制灯工艺对卤粉性能的影响并分析其原因,从而为改进卤粉应用特性和为消除不合理的制灯工艺对卤粉带来的有害影响,进而为提高荧光灯的光学性能提供有效的实验数据,对于提高灯的性能有着重要的经济价值。     

浸取过磷酸钙制饲料磷酸氢钙的脱氟问题

用过磷酸钙浸出液制取饲料级磷酸氢钙时，由于游离酸高，氟被浸入液相，所以必须脱氟，以保证产品质量。但由于一般脱氟所采用的措施不当，磷损失高，且质量难以达标，利用CaHPO     

氧化钙对电石生产节能的影响

从电石生产工艺出发,分析了氧化钙(俗称白灰)的杂质、生过烧、粒度和粉末率对电石生产节能降耗的影响,并介绍了采取的相应措施。严把白灰原料质量关,科学合理调整配比,可有效提高电石产品质量,降低电石生产成本。     

Effect of process conditions on spray dried calcium carbonate powders for thermal spraying

Powder preparation is an important stage in the production of thermal spray coatings with the desired characteristics. An important powder feature is flowability, which can be adjusted through particle morphology, particle size and size distribution. Combined, these features dictate the quality of the coating produced. To increase a powder's flowability, spherical particles within a particular size range are ideal. One way to achieve this is through spray drying. The aim of the present study was to investigate the effect of spray drying process parameters on the physical properties of calcium carbonate powder, with the goal of producing large, spherical particles ranging between 50 and 100 μm in preparation for thermal spray experiments. A key aspect was the use of ethanol to aide in the production of large spheres. A 2³ factorial design of experiments (DoE) was utilised to study the following process parameters: gas flow rate, feed flow rate and solids loading. The resulting powders were characterised in terms of particle size, morphology and production yield. Porous, hollow, spherical particles were produced in a suitable size range for thermal spraying, which was attributed to the rapid evaporation of ethanol. Statistical analysis was utilised to interpret trends between the spray drying parameters and powder characteristics quantitatively.     

在Ca2+-Na2CO3体系中磷灰石与石英浮选分离的溶液化学研究

利用单矿物浮选试验和X衍射光电子能谱(XPS)分析,结合溶液化学计算,研究了以油酸钠为捕收剂时,Ca<'2+>和CO<,3><'2->对磷灰石和石英单矿物浮选的作用机理.结果表明,在以碳酸钠为pH调整剂且凋浆到pH=10左右时,磷灰石的活性成分为CaHPO<,4>,添加的Ca<'2+>与溶液中的溶解组分结合生成的物质与...     

碳酸钙改性聚苯乙烯的初步选择性激光烧结实验

针对选择性激光烧结(SLS)成型的高分子粉末烧结件尺寸精度差、强度低的问题,以聚苯乙烯(PS)为基体粉末,探讨了不同扫描速度下铝酸酯偶联剂处理前后的碳酸钙对PS粉末烧结性能的影响。结果表明,随扫描速度的增加,烧结件的尺寸精度提高、弯曲强度降低;未经处理的碳酸钙对PS烧结件的尺寸精度没有影响,反而降低了弯曲强度;经铝酸酯处理的碳酸钙在一定程度上提高了PS烧结件的尺寸精度和弯曲强度,当扫描速度为1 500 mm/s时,添加质量分数为2%的经铝酸酯处理的碳酸钙,PS烧结件的Z向高度相对误差为4.25%,较纯PS烧结件减少了48.5%,弯曲强度达到6.32 MPa,比纯PS烧结件提高了18.4%,但当扫描速度提高到1 800,2 000 mm/s时,两者之间的弯曲强度差异变小。     

Reaction mechanism and size control of CaB6 micron powder synthesized by the boroncarbide method

Reaction synthesis mechanism of Calcium hexaboride (CaB₆) powder was investigated by using CaCO₃-B₄C-C system. Micron-scale CaCO₃ and B₄C powders were used as main raw materials. The synthesized powder was determined by X-ray diffraction, showing no left reactants if enough CaCO₃ was added to compensate the evaporation of calcium atoms at high temperature. The powder morphology was observed through SEM. The synthesized CaB₆ powder formed hard agglomerates which consisted of cubic CaB₆ crystallites when the reaction completely finished. Reaction process was illustrated indicating it was a solid-state reaction occurred from B₄C surface to the centre. The dry high-energy ball milling was used to investigate the influence of ball-milling time on the shape and size of powder particles. The particle granularity was measured by laser size analysis method. It is obvious that the particles were refined greatly after ball milling for 8 h. However, the CaB₆ powder could not been refined markedly after 16 h. Finally, optimized parameters for size controlling were given in this paper.     

Non-isothermal decomposition kinetics of nano-scale CaCO3 as a function of particle size variation

We report the synthesis of nanocrystalline calcium carbonate with varying particle sizes by precipitation techniques from an aqueous solution of calcium nitrate and sodium carbonate at controlled pH. The particle size of the carbonate powder was precisely controlled by changing the precursor concentration. The synthesized carbonate powders were characterized by using scanning electron microscopy, X-ray diffraction technique, and transmission electron microscopy. The particle size, along with the crystallite size of as-synthesized carbonate powder, decreases with increasing precursor concentration. The non-isothermal decomposition kinetics of the carbonate powder was also evaluated by using near to the modified Arrhenius equation's exact solution. The experimental results were best fitted at n = 0.5, and the one-dimensional diffusion-controlled transport process mechanism (D₁) and one-dimensional phase boundary movement mechanism (R₁) was found to be very close fit of the corresponding evaluated g(α) value. The apparent activation energy of the nano calcium carbonate decomposition was found in the range of 120–175 kJ/mol, which is also inherently functioning with the average particle size. The apparent activation energy of decomposition of CaCO₃ found to be decreased with decreasing average particle size of nanocrystalline calcium carbonate.     

A method for evaluating the acceptability of light sources for clinical visual evaluation of cyanosis

The accurate identification of cyanosis depends on a number of factors including the quality and quantity of the lighting used. Requirements framed in terms of permissible limits on correlated colour temperature and colour-rendering indices worked satisfactorily for many years. However, the demise of halophosphate fluorescent lamp technology and its replacement with triphosphor technology has led to a need to reevaluate the former methods and acceptance criteria. The experimental methods of assessing previous light sources were long and involved. It is impractical to replicate them as each new light source or new lighting technology is developed. There is a need, therefore, for a colorimetric method of assessing light sources for this purpose. In this study, the spectral reflectance characteristics of blood with oxygen saturation levels from 95.6–0.7% are used to calculate colour changes with respect to a reference illuminant and correlated with the results of an extensive study, some years ago, of the influence of light sources in the detection of cyanosis. The results lead to a method of evaluation with a single value criterion for acceptability. The method lends itself to simple modeling techniques for phosphor mixtures and should simplify the design of appropriate fluorescent tube sources for clinical visual evaluation of cyanosis. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23, 4–17, 1998.